# Slight hickup



## John-H (Jul 13, 2005)

If I drive in 4th at 40mph and then put my foot down, I get the usual turbo spool up and surge of power but I also get a slight hickup (momentary loss of power) as the engine passes through 3,000 rpm. Power is normal above 3,000 rpm. The hickup is repeatable. It does this with aircon off or on. Outside air temp is high.

The car has had a full service and cam belt change recently but I'm not thinking it's related as it drives normally generally.

I get no VAG-COM errors or warning lights. No other symptoms apart from a slight loss of power in these high temperatures. Anybody experienced this hickup? - any ideas before I go delving? Thanks.


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## XTR (Mar 2, 2006)

I had an engine management light on the other day..... Checked with VAGCOM and it said, fuel system, running lean. Cleared the fault and took the car for a blast..... 2nd gear, aircon on, and the car kept hickuping.... until it got past 4k rpm then it settled down and the sudden surge of power came in!!!!

Never done it since so unsure what was up for it that moment!


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## KenTT (Feb 20, 2005)

John-H said:


> If I drive in 4th at 40mph and then put my foot down, I get the usual turbo spool up and surge of power but I also get a slight hickup (momentary loss of power) as the engine passes through 3,000 rpm. Power is normal above 3,000 rpm. The hickup is repeatable. It does this with aircon off or on. Outside air temp is high.
> 
> The car has had a full service and cam belt change recently but I'm not thinking it's related as it drives normally generally.
> 
> I get no VAG-COM errors or warning lights. No other symptoms apart from a slight loss of power in these high temperatures. Anybody experienced this hickup? - any ideas before I go delving? Thanks.


Hi John

Did you change the spark plugs :?:

Does this happen when the car is coming up to normal temp or at full working temp :?: , as I had something like this on my A3 T sport, turned out to be a temp sensor.

Also I assume you have also tried unpluging your MAF.


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## Wak (May 6, 2002)

as ken says try the maf unplug as well!


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## John-H (Jul 13, 2005)

Hi Guys,

I did replace the spark plugs in the major 40k mile service and the hickup happens when at running temperature.

I'll repeat the test with the MAF unplugged but it's only one year old today! (25th July) :lol: It didn't make any difference a month ago when I thought it was running a little jerky and I put it down to my imagination.

One other thing I noticed; I found it difficult to hold the revs at 2,000 rpm whilst doing the aircon test the other day. Either the aircon compressor was loading the engine and causing the revs to change, or, I'm wondering if I'm getting early signs of lambda sensor failure. I'll try some logging but I may have to get a scope on it as it's a narrow band sensor.


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## KenTT (Feb 20, 2005)

John-H said:


> Hi Guys,
> 
> I did replace the spark plugs in the major 40k mile service and the hickup happens when at running temperature.
> 
> ...


Now your talking. is that dual trace :wink:


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## John-H (Jul 13, 2005)

It's a four channel analogue storage scope - very useful for looking at lambdas


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## John-H (Jul 13, 2005)

Tried it again today. It wasn't as hot which might have made a difference and indeed the hickup was less pronounced but still there.

I then tried it with the MAF disconnected. The hickup was now gone and you just noticed the turbo picked up nicely instead.

I then re-connected the MAF but also pulled the ECU fuses to reset it - and guess what? Also no hickup :roll: Seems OK now - so I don't know.


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## John-H (Jul 13, 2005)

Can anyone tell me where the transition point from vacuum to boost occurs in these circumstances (40mph, 4th gear, foot hard down - what revs?) as I haven't got a boost gauge? Just wondering if it's related to the hickup :-| Could there be a sticky sensor or something?

Seems to be less pronounced in colder temperatures


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## KenTT (Feb 20, 2005)

John-H said:


> Tried it again today. It wasn't as hot which might have made a difference and indeed the hickup was less pronounced but still there.
> 
> *I then tried it with the MAF disconnected. The hickup was now gone and you just noticed the turbo picked up nicely instead.
> 
> I then re-connected the MAF but also pulled the ECU fuses to reset it - and guess what? Also no hickup *:roll: Seems OK now - so I don't know.


Hi John

Oh the joys of diagnoses, normally something you excel at. This is unlike you  , I bet on any other day you would have tried to eliminate one component at a time and not two.

Still might be that temp sensor you know :wink:

PS Iâ€™ll post those bushes tomorrow.


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## John-H (Jul 13, 2005)

Hi Ken,

Temp sensor... hmmm... two things at once... hmmm.... I know :roll:

Oh, and thanks again you're a gent sir :!:


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## nolive (Aug 5, 2004)

John-H said:


> Can anyone tell me where the transition point from vacuum to boost occurs in these circumstances (40mph, 4th gear, foot hard down - what revs?) as I haven't got a boost gauge? Just wondering if it's related to the hickup :-| Could there be a sticky sensor or something?
> 
> Seems to be less pronounced in colder temperatures


Hi John,

on my AMD remapped engine, this slight but noticeable hick-up appears also at 3,000rpm but espcially in second gear 30mph ishwhen you floor it.

I was planning to investigate that problem, in the next few days or over the week-end, now that I've got some time.

I will start with some runs with the two MAFs I have. Then will test new plugs since I'm servicing the car at the same time and also play a bit with the Hyperboost DV I'm running at the moment.

Not to mention the temp sensor aswell :roll: even if I doubt it may have any impact on the issue but you never know until you test it, don't you 

I will let you know

olivier


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## John-H (Jul 13, 2005)

Hi Olivier,

So how did you get on with your temp sensors? Interesting that you have a hickup too. Mine is not noticible most of the time espescially in normal driving and seems to go away if you change something like unplugging the MAF or ECU reset. I only found it again when I went looking. Got to thinking it may be the transition point. I'd be interested to hear what you find.


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## nolive (Aug 5, 2004)

John-H said:


> Hi Olivier,
> 
> So how did you get on with your temp sensors? Interesting that you have a hickup too. Mine is not noticible most of the time espescially in normal driving and seems to go away if you change something like unplugging the MAF or ECU reset. I only found it again when I went looking. Got to thinking it may be the transition point. I'd be interested to hear what you find.


Hi John,

I've made some runs last night with the two MAf I've got available and I'm embarassed to say that the hickup is not present or better said the transient point at 3,000rpm is now not noticible.

since I came back from Wales last week-end, I've refueled the car with BP ultimate as oppsoed to Optimax or Tesco 99. is it why it's running smoother? is it because of the lower temperatures we are experiencing in London recently?

i'm confused to be honest. what about yours then?

Olivier


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## John-H (Jul 13, 2005)

Mine's been fine too - could be air temp related :wink:


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## Elmbo (Nov 21, 2005)

John-H said:


> If I drive in 4th at 40mph and then put my foot down, I get the usual turbo spool up and surge of power but I also get a slight hickup (momentary loss of power) as the engine passes through 3,000 rpm. Power is normal above 3,000 rpm. The hickup is repeatable. It does this with aircon off or on. Outside air temp is high.
> 
> The car has had a full service and cam belt change recently but I'm not thinking it's related as it drives normally generally.
> 
> I get no VAG-COM errors or warning lights. No other symptoms apart from a slight loss of power in these high temperatures. Anybody experienced this hickup? - any ideas before I go delving? Thanks.


Hi John,

Amazingly enough, IÂ´m experiencing exactly the same thing for a while now! IÂ´ve even replaced the MAF but the problem stayed.... Very annoying. I also notice that after the hickup, power does not come on as fast as I would expect. If I slowly pull back the throttle is suddenly starts to pull like a mule again. So less throttle gives me more power (??). Is that happening to you too by any chance?

IÂ´m dying to find the solution for this.


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## Elmbo (Nov 21, 2005)

John-H said:


> Mine's been fine too - could be air temp related :wink:


P.S. Did you have an APX engine or a BAM? I have an APX....


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## John-H (Jul 13, 2005)

Hi Elmer,

Mine is an APX too. I was wondering if the hickup was the transition point from vacuum to boost but I haven't got a vacuum gauge so I can't easily tell. I thought maybe there was a sensor or something to look at or even get VAG-COM on it but the broblem seems to have gone away now, so I'm guessing it was air temperature related and now things are cooler it's better behaved.


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## John-H (Jul 13, 2005)

Oh and - yes about the throttle - as it's fly by wire you don't really know what it's doing. VAG-COM may have an output value so it might be possible to log throttle pedal position, butterfly position, boost and torque but I haven't looked to see if you can.


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## gt russell (Nov 27, 2005)

John I wasgoing to mension the temp sensor . Mine immediatley ran better when I changed it


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## gt russell (Nov 27, 2005)

I forgot to mension that mine is APX engine also


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## KenTT (Feb 20, 2005)

gt russell said:


> John I wasgoing to mension the temp sensor . Mine immediatley ran better when I changed it


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## John-H (Jul 13, 2005)

That's what Ken said Russell (as Ken has just pointed out :lol: ) Only my Aircon trick 49C coolant temp figures are ~92 to ~94 deg C. normal running which seems about right I thought. I'll try to check it further but I don't think it looks too far out. I can't remember what the thermostat marked temperature is but there will be a slight difference. What did your 49C read before you changed the sensor?


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## gt russell (Nov 27, 2005)

oh my god min is 87-90 I bet my thermostat is on its way out now ! bloody typical :lol:


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## gt russell (Nov 27, 2005)

I forgot about ken TT mensioning the temp sensor I also forgot to tell you I had a brain hemhorage 6 years ago (seriousley ) and they didnt hard wire me after the surgery :lol: :lol:


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## KenTT (Feb 20, 2005)

gt russell said:


> I forgot about ken TT mensioning the temp sensor I also forgot to tell you I had a brain hemhorage 6 years ago (seriousley ) and they didnt hard wire me after the surgery :lol: :lol:


 :lol: :lol:

Hi Russell, Your lucky you have one to hemhorage, I'm not sure I ever had one :lol: . I just like to pull John's leg sometimes.


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## Elmbo (Nov 21, 2005)

John-H said:


> Hi Elmer,
> 
> Mine is an APX too. I was wondering if the hickup was the transition point from vacuum to boost but I haven't got a vacuum gauge so I can't easily tell. I thought maybe there was a sensor or something to look at or even get VAG-COM on it but the broblem seems to have gone away now, so I'm guessing it was air temperature related and now things are cooler it's better behaved.


So you reset the ECU and the problem went away. Could you tell me which fuses I need to pull?


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## John-H (Jul 13, 2005)

Fuse 10 - and as I wasn't too sure, everything that said "engine petrol" etc. but the problem might have gone away as the engine had cooled in the meantime etc. The problem was less pronounced but seems to have disappeareed now the weather is cooler.


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## Firefox (Sep 9, 2005)

[/quote]*Amazingly enough, IÂ´m experiencing exactly the same thing for a while now! IÂ´ve even replaced the MAF but the problem stayed.... Very annoying. I also notice that after the hickup, power does not come on as fast as I would expect. If I slowly pull back the throttle is suddenly starts to pull like a mule again. So less throttle gives me more power (??). Is that happening to you too by any chance?

IÂ´m dying to find the solution for this.[/quote]*

Hi,

My BAM engine does exactly the same thing, sometimes if I floor the accelerator, there is nowhere near as much power as there should be, then if I back off slightly, it flies. It doesnt happen if I accelerate gradually though! :?

Mine is re-mapped with a Forge DV, but it did it before the re-map

Weird!

Anyone got any ideas?

8)


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## Elmbo (Nov 21, 2005)

*Amazingly enough, IÂ´m experiencing exactly the same thing for a while now! IÂ´ve even replaced the MAF but the problem stayed.... Very annoying. I also notice that after the hickup, power does not come on as fast as I would expect. If I slowly pull back the throttle is suddenly starts to pull like a mule again. So less throttle gives me more power (??). Is that happening to you too by any chance?

IÂ´m dying to find the solution for this.[/quote]*

Hi,

My BAM engine does exactly the same thing, sometimes if I floor the accelerator, there is nowhere near as much power as there should be, then if I back off slightly, it flies. It doesnt happen if I accelerate gradually though! :?

Mine is re-mapped with a Forge DV, but it did it before the re-map

Weird!

Anyone got any ideas?

8)[/quote]

Sounds exactly like what IÂ´m experiencing. Gone start pulling fuses first


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## Elmbo (Nov 21, 2005)

Wanted to give this thread another jump start. The hickup doesn't seem to want to go away. If I reset the ECU it becomes less noticable for a while, but then gradually comes back.

I've still got the strange phenomena that when flooring the accelerator, between 3 and 4k revs in 4th gear or up the car seems to be holding back. If I slowly come off the accelerator in that rev range, it suddenly picks up and the car just flies forward.

Does anybody have an idea of what could be going on? What could the ecu be "thinking"? I've now got the hang of it and know how to make the car pull hard, but I'd rather the ECU does this for me!

Appreciate you input


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## Firefox (Sep 9, 2005)

still no further with mine either.

I get the feeling it is over boosting and being held back by the ECU??


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## TTCool (Feb 7, 2005)

Good morning

I've had this since I had the re-map. Slightly less throttle, more power. I now know how to use the throttle for the best advantage, but I'd rather slap the floor boards. It takes away a little of the pleasure :roll: I've had conversations with AMD as they did the re-map, but it all sounds like waffle to me. Why can't it be mapped out of the equation, everything else has. :?

Joe


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## TTCool (Feb 7, 2005)

By the way, everything else is a smooth as a baby's bottie. I just have to regard full throttle as 98% of travel. If you know what I mean.

Joe


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## Firefox (Sep 9, 2005)

Good point Joe!

It does take some of the fun away, as you are always concious that you may not get maximum acceleration (in fact quite a bit less), which can be frustrating!

I agree that it should have been ironed out, we pay Â£500+ for an hours work, but apparently we are paying for 100's of hours development on the dyno, yeah right! (this is not a dig at AMD by the way, as I don't have an AMD re-map)

We are probably expecting too much from something generic, Iam a great advocate of the Dave Walker (of Emerald) view on mapping and engine management.

Think I will just continue changing bits and bobs and tweaking where I can to try to overcome this.

8)


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## TTCool (Feb 7, 2005)

Firefox said:


> Good point Joe!
> 
> It does take some of the fun away, as you are always concious that you may not get maximum acceleration (in fact quite a bit less), which can be frustrating!
> 
> ...


I paid Â£750. It was a custom re-map, not generic; rollers before and after etc.


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## Firefox (Sep 9, 2005)

Sorry Joe, I was a bit presumptuous then.

In a way thats even worse, as they should have mapped it at all throttle openings / rpm's?

What explanation did AMD give you Joe, it would be nice to know.

8)


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## nolive (Aug 5, 2004)

TTCool said:


> Firefox said:
> 
> 
> > Good point Joe!
> ...


Joe,

I paid only 400Â£ for my AMD custom remap :wink: (special offer at the time) :lol: but sill have the same feeling about the throttle ease to get more power.

quite frustrating I agree....

like for the hick-up originally mentionned on this thread by John, it really occurs when temperatures are high though.

i've got two weeks in the South of France now(with nice and warm weather planned  ) to find out what I can do, if any, to improve this.

we'll see

Olivier


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## Elmbo (Nov 21, 2005)

Glad to know this is not uncommon. I too have a custom remap. But itÂ´s frustrating that the cause cannot be determined.... **sigh**

Well, if any brilliant ideas arrise, please post...


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## TTCool (Feb 7, 2005)

One chap on another forum, I think, suggested that we should put a little spacer in that bolt under the accelerator pedal which would presumably coincide with the correct amount of welly for best performance. :lol: :lol:

Just maybe

Joe 8)


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## a18eem (Sep 24, 2005)

Wak said:


> as ken says try the maf unplug as well!


Yep ! exactly what I would say!! :wink:


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## Elmbo (Nov 21, 2005)

a18eem said:


> Wak said:
> 
> 
> > as ken says try the maf unplug as well!
> ...


Been there, done that, bought a T-shirt.... My MAF is brand new by the way...


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## John-H (Jul 13, 2005)

Hi Elmer, Joe, Olivier and everybody 

You describe exactly what mine did Elmer. Reset the ECU and it goes away but slowly comes back - whilst the weather was hot. Olivier, I too find it's gone away with the lower temperatures. Interesting about the throttle lift off more power thing. It would be interesting to see the actual throttle position as your foot position will not correspond. Possibly VAG-COM might have a measuring block for this.

I can't really add anything to that other than I'm off for some more driving on the brilliant roads around Sutherland


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## TTCool (Feb 7, 2005)

Good morning John

Where is Sutherland. Please tell. I can't get enough of brilliant roads 

Joe


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## John-H (Jul 13, 2005)

Good evening Joe. Sorry, been out and only have a few minutes of Orange extra to go before my laptop turns into a pumpkin. The A9 from Inverness to Thurso is a fantastic road, as are many A and B roads around Sutherland in the Scottish Highlands. The traffic is so light round here driving is such a pleasure and the scenery is to die for. Might go over the other side to Ullapool tomorrow or climb up Ben Braggie again. The only problem is Inverness is the only place I know to get Shell Optimax or BP Ultimate and I've only got one bottle of octane booster with me for emergencies.


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## MikeyG (Sep 17, 2005)

John-H said:


> Good evening Joe. Sorry, been out and only have a few minutes of Orange extra to go before my laptop turns into a pumpkin. The A9 from Inverness to Thurso is a fantastic road, as are many A and B roads around Sutherland in the Scottish Highlands. The traffic is so light round here driving is such a pleasure and the scenery is to die for. Might go over the other side to Ullapool tomorrow or climb up Ben Braggie again. The only problem is Inverness is the only place I know to get Shell Optimax or BP Ultimate and I've only got one bottle of octane booster with me for emergencies.


That sounds familiar John - having to go to the Shell station in Inverness twice a day! Whilst it doesn't do Optimax, the Shell station at Ullapool (on the right half a mile short of the town) *does have Shell 98 ron fuel*. If you get over that way, get yourself up the A837 and round Loch Assynt - great scenery and good roads (my sig pic was taken there).


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## John-H (Jul 13, 2005)

Hi Mike,

Thanks for the tip about the Shell station. I did see you can do a search for Optimax on the Shell website but it doesn't come up with your 98 option. Might give that one a try. I only managed 22mpg over the last couple of days and I thought that was bad - you must have been doing some miles to visit twice a day  Nice sig pic BTW :wink:

Oh... and hy hesitation seems not to have resurfaced. I've been trying to reproduce the lift off boost thing, which I have noticed on the odd occasion before but that seems not to be too obvious either. I'm not sure if the surge in power is more to do with when the boost pressure comes up and if you happen coincidentally to lift off at that moment, making you think that part throttle gives more power - when I've tried to reproduce it and got the surge in power, putting my foot back down again does not reduce the power.


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## John-H (Jul 13, 2005)

I think I've made a little progress on this. I've discovered that I can reproduce the "hickup" at part throttle and when first I've let the turbo spool down.

What I did was drive in 4th gear at about 3,500 rpm, let the revs drop on overrun to 2,500 rpm (by this time the turbo has stopped spinning). I then put my foot down but only part way and noticed that when the revs pass ~3,000 rpm the hickup occurs. It's worse for smaller throttle openings and with 100% throttle is barely noticable.

It also doesn't happen if you give a bit of 100% throttle (to spin the turbo) then back off the throttle to partway - you don't get the hickup at 3,000 rpm as the revs climb. Allowing the revs to climb from lower than 2,500 rpm also reduces the hickup (presumably allowing more turbo spool up time). Also, only overrunning down to 2,700 rpm (but from higher up) makes it worse as the revs pass up through 3,000 rpm (there's hardly been any spool up time).

So it seems to be turbo speed related. I've tried to capture three throttle settings for this condition but the poor sampling rate and consequent uncertainty makes it unclear. I thought of doing it in 5th or 6th to slow things down but of course the turbo would have longer to spool up and it might not do it. I might try this again with less measuring blocks, with just one group, in order to get better sampling. It seems to show less ignition advance along with the lower manifold pressure perhaps? I wonder if something in the map is presuming the turbo is spinning when it isn't???

I'm also wondering if any headway could be made by fiddling with DV springs - what do you think?


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## cyberdude (May 24, 2002)

John, what you describe is basically what's happening to me too. I notice the hickup most when I approach a couple of the large roundabouts near me. I drop it into 4th slowing down on entering the roundabout (revs falling to around 2K- 2.5K and then start to accelerate through the round about where my rpm rises to around 3K just as I exit and I get the hickup.

Did you log any timings and timing corrections? Just wondering if you're seeing the same timing issues as I have at the 3,000rpm area.


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## John-H (Jul 13, 2005)

cyberdude said:


> John, what you describe is basically what's happening to me too. I notice the hickup most when I approach a couple of the large roundabouts near me. I drop it into 4th slowing down on entering the roundabout (revs falling to around 2K- 2.5K and then start to accelerate through the round about where my rpm rises to around 3K just as I exit and I get the hickup.
> 
> Did you log any timings and timing corrections? Just wondering if you're seeing the same timing issues as I have at the 3,000rpm area.


No, only the BTDC figure. What blocks were you measuring and what did you see? Have you got anything you could post up?


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## cyberdude (May 24, 2002)

John.

I measured the BTDC and the timing corrections. Something funny happens with BTDC at around 3100rpm and also there seems to be a lot of timing corrections going on with Cyls 2,3 & 4. I get pretty much consistent readings when doing multiple runs (I have shown the worse case here). My BTDC readings varied between -0.8 to -1.5 @~3100rpm and the timing corrections seemed to vary across which cylinders were being corrected. I'd be interested to see what your BTDC and timing corrections are.


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## skydiver (Oct 12, 2006)

I was having this issue as well with my car. I ended up getting fed up and took it to Star performance and went out with Jim in the car with vag-com connected. I had a couple of fault codes that were easily reset and the only other thing that stood out was the Maf readings.

A new Maf was installed and it cured the problem. I had actually tried the Maf disconnect trick previously but it made no difference but the new Maf has cured it.

Dave


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## John-H (Jul 13, 2005)

Cyberdude, Thanks for that. I'll have to try some more logging and see what mine says. Nice table by the way :wink: .

Skydiver, I'm glad you've got rid of your problem. Sorry I wasn't able to help but it did sound as though your hickup was bigger than mine. Can you do me a favour please?

Try driving in 4th at 3,500 rpm, then take your foot completely off the accelerator and let the car slow under engine braking to 2,500 rpm (the turbo will now have stopped spinning). Now put your foot half way down and hold this throttle position. Note what happens when the engine gets to 3,000 rpm - do you get a hickup? Even slight? Try it a few times with different throttle positions. I find less throttle makes the hickup worse.

I'm wondering if you will now be able to reproduce what I found a couple of posts back. It could be a general problem which you had worse because of a faulty MAF or perhaps we all need new MAFs? :wink:


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## skydiver (Oct 12, 2006)

Hi John,

I always found my problem worse when applying full throttle, only using part throttle made i better. That said I will go out in the car later and test as you suggest and let you know the result later.

Dave


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## John-H (Jul 13, 2005)

Cheers Dave


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## skydiver (Oct 12, 2006)

Hiya John,

Well I took the car out this morning and testing it in fourth at all different throttle positions and with no hick-up. I also tested it in 5th puting it on full load and again no hick-up.

My problem at tmes was pretty severe, in 5th it would sometime "hunt" at 3000 rpm now nothing.

Dave


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## John-H (Jul 13, 2005)

Thanks for that Dave. I guess it might be worth swapping with another MAF to see if it makes any difference. My MAF is only about a year old though.


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## skydiver (Oct 12, 2006)

I would also like to know the percentage of cars that have this problem and are remaped?

I think it could be linked to that to be honest. I have a pretty poor map in my car with a big dip in the boost between 3000-4000 rpm I never knew it was on the car when I bought it. The first I knew of it was when I went to get it remaped and was told it was already done.

I am gonna get a much better map installed though at Star performance, probably GIAC...


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## bagseye (Dec 23, 2006)

i have the same sort of thing on my 225. only just started to experience it now so ive not had chance to check it out. 1st-2nd is fine but from 2nd-3rd foot to the floor there is a slight dip in power or lag then it boosts up.once again id put this in the 3000-4000 rev range

i did have a trial re map done and it seems to have kicked in after that expired

however if i am driving normally there seems to be no problem

as i have some time this weekend does someone have the link to maybe help reset this problem


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## John-H (Jul 13, 2005)

bagseye said:


> i have the same sort of thing on my 225. only just started to experience it now so ive not had chance to check it out. 1st-2nd is fine but from 2nd-3rd foot to the floor there is a slight dip in power or lag then it boosts up.once again id put this in the 3000-4000 rev range
> 
> i did have a trial re map done and it seems to have kicked in after that expired
> 
> ...


Was it a Revo trial?


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## cyberdude (May 24, 2002)

So John, have you had a chance to log the timings yet? I am keen to see how they compare with what I am getting.

Also, I'd appreciate it if someone, when they have time, can log the same blocks on a car that is running normally so I can see what the timing values should look like. Because I can't make sense of what's happening with mine.


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## bagseye (Dec 23, 2006)

> ="John-H
> Was it a Revo trial?


i beleive so. but i havent got back to the garage yet to find out for sure


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## John-H (Jul 13, 2005)

cyberdude said:


> So John, have you had a chance to log the timings yet? I am keen to see how they compare with what I am getting.
> 
> Also, I'd appreciate it if someone, when they have time, can log the same blocks on a car that is running normally so I can see what the timing values should look like. Because I can't make sense of what's happening with mine.


No, sorry I've not had time yet :?



bagseye said:


> > ="John-H
> > Was it a Revo trial?
> 
> 
> i beleive so. but i havent got back to the garage yet to find out for sure


If it is a Revo map there might be difficulties due to Revo software not reverting back to stock even after the 5 hour trial time-out. Allegedly it leaves a 225 with only 200bhp (possibly to make you more likely to buy the full thing!). This has been reported a number of times. It also leaves extra software in memory that was not there in the original Audi stock code. This extra code can cause problems when uploading a new map requiring a tuner to first replace it with stock code.


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## bagseye (Dec 23, 2006)

is there a way to reset the ecu to the original settings without causing too much disturbance to the car?


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## John-H (Jul 13, 2005)

Unfortunately although you can "reset" the ECU by pulling fuse 10 (pre 10.2001) or fuse 37 (post 10.2001) all this does is clear out the volatile RAM memory where temporary learned parameters are stored. These are the "adaptation values" which are rolling average settings learned from the fuel octane, driving style, engine condition etc. If you pull the fuse for a few minutes, the adaptation values are lost which forces the ECU to relearn from scratch.

Pulling the fuse does not, however, get rid of a remap or the residuals of the Revo trial, as the remap is stored in non-volatile FLASH memory which requires specialist equipment to re-write.

Revo add a timer function into the original code as well as introduce a new map of timing and boost parameters. When the trial expires the map is supposed to revert to stock, supposedly by changing the map values back to standard. This is what they say, but I know there is no way the timer function and the hooks into the original code are going to be deleted even if the original map was re-instated. It's too risky to write a self deleting programme - far easier to just switch things off.

This leaves two problems. Firstly, because the expired Revo trial leaves residuals in the code, the software is now non standard. This causes subsequent tuner's re-map attempts to fail because their uploading checks require standard previous code. They first have to upload a standard map and start afresh. Secondly, a number of people have reported running a rolling road test after the Revo trial has expired and found their 225bhp TT is more like a 200bhp TT. Whether this is just an error or a marketing/sales ploy is an interesting question.

You'd best go back to Revo and ask them to upload a standard map back on the car and don't be fobbed off by claims of it all having reverted to stock automatically - that's not the case.


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## bagseye (Dec 23, 2006)

cheers for the info


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## John-H (Jul 13, 2005)

Cyberdude,

Sorry for not coming back with some logging results. I tried it on the way home from work last night but the roads were so conjested I couldn't repeat your sustained run - presumably you were in a high gear?

I did notice however that, consistent with my previous testing, I did not get the "hickup" in 5th or 6th gear on the motorway even if I had a significant overrun to stop the turbo - I guess it just spools up in the extra time as the engine revs rise through 3,000 rpm.

I could easily repeat the "hickup" in 4th gear on quieter B roads later however as I did before. Being in 4th the time to pass through 3,000 rpm is much less and I don't get as many samples though.

Unfortunately the log file results were not clear. I'll try it again over the weekend when the motorway is less conjested.


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## cyberdude (May 24, 2002)

Hi John

My logs were done in 4th gear. I feel the hickup most in 4th. A couple of days ago while I was on the motorway I was trying to see if I could feel the hickup in 5th and 6th (no logging) and found the results inconsistent. Sometimes I felt nothing other times I did feel the hickup. I'll go out on the weekend and log the 5th and 6th gear runs to see if anything shows up. I'm hoping that in 5th and 6th I'll catch more samples of the problem.


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## John-H (Jul 13, 2005)

Mine's worse in 4th too. I did think more samples would be taken in 5th or 6th but it doesn't seem to hickup in the two top gears :? . I think that's because the turbo has longer to spin up.

Do the 4th gear results, you posted, coincide with a hickup? I found mine didn't hickup if I allowed more time for the turbo to spin up e.g. from 2,000 rpm. Mine only hickups after a long overrun and accelerating from as little under 3,000 rpm as possible. I'll try and reproduce your results though, in the same conditions, for a comparison.


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## cyberdude (May 24, 2002)

Yes those results coincided with a hickup. I've not really noticed if the hickup is worse when accelerating from just under 3000 rpm than from 2000 rpm. I'll give that a try when I next go out.

Next time I go out I may try logging those blocks in the following circumstances. (All in 4th gear)

Cruise at 2000 rpm then accelerate through 3000 rpm.
Cruise at just under 3000 rpm then accelerate through 3000 rpm.
Overrun from 4500 rpm to 2000 rpm then accelerate through 3000rpm.
Overrun from 4500 rpm to just under 3000 rpm then accelerate through 3000rpm.

Don't know if that will highlight anything of value.


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## John-H (Jul 13, 2005)

If it's like mine it might show up that a stalled turbo makes it worse :wink:


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## John-H (Jul 13, 2005)

cyberdude said:


> John.
> 
> I measured the BTDC and the timing corrections. Something funny happens with BTDC at around 3100rpm and also there seems to be a lot of timing corrections going on with Cyls 2,3 & 4. I get pretty much consistent readings when doing multiple runs (I have shown the worse case here). My BTDC readings varied between -0.8 to -1.5 @~3100rpm and the timing corrections seemed to vary across which cylinders were being corrected. I'd be interested to see what your BTDC and timing corrections are.


I did some more successful logging yesterday. This first result tries to repeat your results in similar circumstances:










There has been plenty of time for the turbo to spool up by 3,000 rpm. I still get the BTDC timing to drop to 0 degrees (not -ve like yours) then rise again as it passes through but I don't get a hickup to speak of here. I do get timing corrections at high revs but not at 3,000 rpm.

I repeated the same run but this time also looking at turbo pressure. You can see in this result the manifold pressure matches the command pressure well before 3,000 rpm and that the command pressure drops off at high revs.










The result below, which does correspond with a "hickup" at about 3,000 rpm (after a long overrun down to 2,720 rpm), show the manifild pressure is lagging behind the command pressure at 3,000 rpm, due to the overrun, which has caused the turbo to stall. The BTDC has also changed radically from 21 deg., at initial throttle opening to, I presume, 0 deg., at just under 3,000 rpm but where also the manifold pressure is lagging the command pressure by quite a bit. I thought I was logging throttle pedal position but it might be the actual throttle position seeing as it goes to 100% when I was sure I was only pressing the pedal part way.










I'm not sure why your BTDC figure goes negative. My log results never do this - they only go to zero. Also your timing corrections appear through the rev range, unlike mine which appear mostly at high revs. Occasionally I get the odd smattering of correction at other times.

Have you tried logging your turbo pressure?

I think the hickup I get on mine is just to do with turbo stall, which could possibly be improved by fiddling with spring rates on the DV perhaps?

I'm wondering if yours is due to your knock sensors retarding the ignition now or in the past and changing the adaptation values. Have you tried resetting the ECU?


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## cyberdude (May 24, 2002)

Hi John

Interesting logs. Well they show at least that my timing becoming negative at 3000 rpm probably isn't normal.

I'll log the knock sensors and see what they say but I'm not getting any errors throws for them.

I'll log my pressures and mimmick your runs and see how they compare. Were all your runs done in 4th gear?

With regards to throttle opening, I found the same thing. Although I didn't have the peddle all the way down the logs showed 100% open so as you say, probably not the peddle position but the actual throttle position.

Is your car remapped or standard?


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## KenTT (Feb 20, 2005)

John-H said:


> Thanks for that Dave. I guess it might be worth swapping with another MAF to see if it makes any difference. My MAF is only about a year old though.


Sorry John, that reminds me I must post that MAF to you. I'll take it out of the housing and send it in a jiffy bag, if thats OK.


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## John-H (Jul 13, 2005)

Cyberdude,

There was another measuring block with both "Throttle" and "Throttle 2" I think and they did seem to be either end of the wire. I suspect the "Throttle" in the above logs is actually the "Throttle 2" in the other block - perhaps there is some confusion with the title. Yes they were all in the same gear and yes it has been remapped. It will be interesting seeing your pressures.

Ken,

Thanks for the offer I'll see if it makes any difference to the results  .


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## John-H (Jul 13, 2005)

I got round to installing Ken's kindly donated MAF (Thanks Ken!) and guess what? The hickup is no more! 

I also did a couple of acceleration runs from 40mph to 60mph in 4th gear down the same level road.

.... My Maf = 4.75 seconds
Ken's MAF = 4.30 seconds

Ken's MAF pulls smoothly, whereas mine seems to cause the engine to faf around not doing much for the first few moments (the Hickup), which is why the timed run takes longer. Once it gets going it pulls OK. Funny thing is this timed run of 4.75 seconds is exactly the same time I measured when I first got the remap in August 2005 when my MAF was only one month old. Looks like it's always had this problem it seems :? . Sadly the MAF is a year and a half old now, so I don't think GSF will be honouring any guarantees  .

For good measure I did a 0-60mph run in 5.65 seconds just off the speedo. I don't want to repeat that too much to save the clutch.

What I did notice however was that Ken's MAF only pulled 160 gm/sec peak whereas my MAF peaked at 220 gm/sec. I did think it was running out of steam at high revs.

According to Wak's site 
.............180 TT - 135-145+g/s 
.............225 TT - 170-180+g/s 
Chipped 225 TT - approx 200-210+g/s

Ken's MAF is reading too low at high flow but I can only believe is more correct than mine at lower flow rates. Perhaps my MAF's calibration curve is offset too high which might explain the slightly high peak figure of 220 g/s. At lower flow the same offset would be a more significant error.

Looking at the logs:

... My MAF @ 880 rpm = 2.94 g/s
Ken's MAF @ 880 rpm = 2.72 g/s

How does this compare with ayone elses?


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## cyberdude (May 24, 2002)

John

Sorry for the delay in getting back but I've been away a lot and haven't had a chance to do any logging.

Yesterday I went for a quick run and logged the long overrun condition - running down from 4000 rpm to ~2700 rpm. I got similar results to you so I think that may be normal. 









I'm still getting the negative timing value at ~3000rpm and also noticed that my timing values are also negative while idling which concerns me as I'm sure this is not correct.

So I decided to see what other measuring blocks I could look at and found the knock sensor readings for cyls 1 & 2 were reading higher voltages than 3 & 4. I did a quick run and found that cyls 1 & 2 were consistently reading higher voltages, at one point almost 7V more than 3 & 4. Does anyone know what the baseline reading should be and what it means when the readings are high or low?









I'm sure my problem is different to yours John as I clearly have some sort of timing issue.

With regards to your question about MAF readings, mine reads 3.27g/s when idling at 880 rpm. I didn't do any runs up to the red line but at 4800 rpm it read at 197g/s and I remember from previous runs it would get to around 208g/s.


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## John-H (Jul 13, 2005)

Hi Cyberdude,

Thanks for the update and sorry for not responding quicker. Regarding your knock sensors. There are only two. One does 1+2 and the other 3+4. I'm not sure what the voltage should be but I think it should be in balance. This might be reflected in the individual cylinder timing corrections. Bentley only says about degrees of timing correction achieved being between 0 and 12 degrees on block 20, 22 and 23. It says to check this after DTC code has been recorded of "Knock recognition control limit reached".

It's possible that your sensors are not torqued down correctly. This is very critical. They should be loosened and re-torqued to exactly 20Nm. It would be worth checking the connectors for corrosion too. Hope that helps.


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## cyberdude (May 24, 2002)

Thanks John. I'll check the torques on the sensors. My problem is slowly getting worse. 

I now also started get the hickup when cruising at between 2300 - 2500rpm when the coolant is warming from around 60C to 90C. While the coolant is in that range the engine seems to miss a beat every 2-3 seconds while in that rev range.

I measured my my Lamda readings and they seemed to be within min / max tolerance although the readings seemed to fluctuate more than expected.

I think I'll get a new MAF and try that just to eliminate it although the readings I'm getting from it seem fine.


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## John-H (Jul 13, 2005)

The lambda readings if it's the earlier narrow band sensor usually snaps between 0.2V and 0.8V about 2 or 3 times a second when cruising making it difficult to monitor with VAG-COM due to the sampling rate. I think later engines use a wideband sensor that produces a more steady reading.


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## boosted (Jun 3, 2007)

Has anyone considered that it could be the clutch slipping?

How do you test for a clutch slipping... find a big hill, drive up it in 4th and see if the revs climb rapidly but the speed doesnt change.

That sounds like what is happening, and it is at 3k, just when the turbo is building boost and trying to put down 250+lb/ft.


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## John-H (Jul 13, 2005)

No, I can assure you it wasn't the clutch slipping. The problem was cured with a new MAF.


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## Chip_iTT (Nov 14, 2003)

John,

For future reference the picoscope website has some interesting automotive tutorials and applications info at: http://www.picotech.com/applications.html

I've used this info to monitor lambda, MAF and abs signals for diagnosis... I have a 2 channel Pico3205 that plugs into the laptop


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## John-H (Jul 13, 2005)

That's interesting Irving. You can get over the slow sampling rate like that  .


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## DuTTchNL (Sep 18, 2010)

I am having the same problem with an APX engine.

Only I can hear unburnded petrol flaming in the exhaust when it is going to hickup...

On the liquid the timing correction really goes up on all 4 cilinders


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## tonksy26 (Jan 31, 2011)

This thread is 5 year old !!!!


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## DuTTchNL (Sep 18, 2010)

tonksy26 said:


> This thread is 5 year old !!!!


This site has a good search engine... haha

It has nothing to do how old the problem is, I just have the same trouble right now!

Going to try to disconnct the MAF on my way home tonight..


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## John-H (Jul 13, 2005)

Five years hey? Only seems like yesterday!

Yes try without your MAF. I replaced mine but I later had similar issues which I traced to faulty coil packs.


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## DuTTchNL (Sep 18, 2010)

Did not make any difference with the MAF disconnected.

Going to try the 2.0T coil packs. Lets see if that makes a difference


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## Nem (Feb 14, 2005)

DuTTchNL said:


> This site has a good search engine...


Quiet! We'll have none of this nonsense talk


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## DuTTchNL (Sep 18, 2010)

Changed Coil pack cilinder 4 and some new plugs..

Runs like a bullet again!!


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