# Over boost problem



## chrisTT-Norwich (Aug 15, 2012)

Hi all, I have still got the same problem with my 225 remapped, when i hit 3000rpm the engine splutters and sometimes i get a misfire. Ok so i have fitted a new MAF got my coil packs replaced under recall.

Vag-com is not throwing up any fault codes. So today i fitted a boost Gauge and it is redlining and appears to be boosting to 26PSI! which is not good! since then i have been driving slowly so i don't ruin my turbo and engine.

Any suggestions what it could be? N75 perhaps? advice would me much appreciated.


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## badger5 (Apr 19, 2003)

chrisTT-Norwich said:


> Hi all, I have still got the same problem with my 225 remapped, when i hit 3000rpm the engine splutters and sometimes i get a misfire. Ok so i have fitted a new MAF got my coil packs replaced under recall.
> 
> Vag-com is not throwing up any fault codes. So today i fitted a boost Gauge and it is redlining and appears to be boosting to 26PSI! which is not good! since then i have been driving slowly so i don't ruin my turbo and engine.
> 
> Any suggestions what it could be? N75 perhaps? advice would me much appreciated.


recent remap?
n75 can cause an overshoot... but if its been there from the remap, its possibly an overshoot in the n75 control?
are the pipes to and from n75 all ok and intact? Does it do it every time? Consistently?

on high load spool, 6th, low rpm plant foot to floor (not how to drive properly mind you) there is a high torque request and this is where the turbo will be spooling the hardest...

spark plugs ? old new gapped ok?


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## chrisTT-Norwich (Aug 15, 2012)

Hi Badger5 the remap was done by the old owner, when i bought the car it went like stink! the problem is nearly all the time now, i occasionally get a good boost, nice strong power delivery but not very often, I have not checked the spark plugs at this stage, will be a job for tomorrow as i have a week off work. Im just a little concerned that this is going to be a potential major problem and cost me a fortune!

Thanks for the swift reply Badger!


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## tony_rigby_uk (Nov 27, 2008)

interesting to know which map.. And what stage.. 26psi doesn't sound too bad.. (have you seen my old post of my boost) n75 could be a issue if it's a brown one. They do create a spike that throws boost error.. Also could be actuator related..as in someone has wound it up for more boost..


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## tricklexxx (Oct 21, 2010)

Mine was over boosting to 29psi which dropped to 24psi when I changed the N75. If you can borrow one that is known to be OK it will help eliminate it.


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## chrisTT-Norwich (Aug 15, 2012)

Think I will buy a multimeter tomorrow and test it  just did a throttle body re-align still getting a rough idle but I'm sure I read somewhere that is normal for a remapped car?


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## TTSPORT666 (Dec 1, 2011)

Chris check the part code on the N75...the last owner might have put an H valve or J valve in. They are prone to spiking.  Just a thought.

Damien.


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## Stealth69 (Jun 25, 2012)

Rough idle on a remapped car?? No mate, that part of the map table is rarely changed so shouldn't be any different to a normal non mapped car.

Over boosting could be down to many things, some already mentioned...... Could simply be down to the cooler weather we have been having.

2bar of pressure constantly is going to see that car in bits soon chap so try to run off boost..... I'd also do some vagcom logging, see what boost the ecu is requesting and what is being served up just to check the boost gauge isn't on the bonk!


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## chrisTT-Norwich (Aug 15, 2012)

I'm new to vag com could you point me in the right direction to a tutorial or give me instructions on now to log the data, I haven't been boosting high recently due to the problem mainly keeping revs low as mainly city driving so I'm hoping the problem is not damaging the car! I'm going to perform a pressure test tomorrow to look for leaks also checking the vac hoses and service my bov too


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## Stealth69 (Jun 25, 2012)

Look on the vcds.. Or was it WAK site mate one of them has a tutorial and it's easy enough to follow 

There will be no damage provided she's not boosting her little heart out.... I doubt there is a leak, you'd see less pressure, not more mate


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## chrisTT-Norwich (Aug 15, 2012)

Just tested my N75 resistance measuring 5 ohms which is not good, think i will try and replace it next


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## chrisTT-Norwich (Aug 15, 2012)

Update, just replaced the n75 no change, cleaned the dirty throttle body, tested waste gate actuator with a compressor all works fine, but still over boosting, when I do over boost the car appears to stutter, could this be the turbo vaine dirty?

I'm at my witts end now! Only thing left to check are the spark plugs and do a vag com check


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## badger5 (Apr 19, 2003)

stutter, could just be spark blowing out @ peak cyl pressure and your high boost
26psi for me is too high... I know some folks say its fine, but imho it aint.. and on these old engines, I think its asking for bent things (rods) and it makes things uber hot, not quick..

new plugs? coils? and logging with vagcom may help get to the bottom of the issue


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## chrisTT-Norwich (Aug 15, 2012)

Thanks badger5 I am really thinking about getting the car un mapped, I'm not really a speed freak so it doesn't suit me. Plugs are next on the list


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## Stealth69 (Jun 25, 2012)

Nothing is leaking and nothing is wrong with that car with the exception that is seems to have a shit unsafe map on it OR it has a bleed valve fitted somewhere, have a nose about for a MBR mate!

the Stutter is more likely to be either not enough fuel as the injectors are maxing out (possibly, not sure what the max for these injectors is), the turbo shitting itself, back pressure because it can't shift the gasses out quick enough..... there are a load of reasons.

I wouldn't have the car unmapped, I'd be tempted to have it remapped...... you don't have to be a speedfreak to want a remap, you could get better fuel economy, more useable power so more torque in the low/mid range to make driving around towns smoother etc...... tell the mapper what you want and they will do it 

Everyone seems to think that more boost = more power, this is NOT the case in can result in lower power, and the car running hotter and as badger said bending rods etc


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## st3v3 (Apr 9, 2007)

i would be tempted to get the map looked at!

IF the injectors are maxed out (and i dont know if they would be) then theres a chance that you could run lean and thats will see you buying new bit that used to look like pistons...or worse.

When you say he mapped it himself, did he write the map, or just upload it from one bought off the net for example, either way youd have thought the boost,fueling and general safety of the engine would have been checked out profesionally after?


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## chrisTT-Norwich (Aug 15, 2012)

He told me he got a tuner near peterbourgh to do it, what I don't understand is the car was driving really well a month ago and not maxing out the boost but now it has changed, can't seem to find the problem. It seems that in 1st and second and occasionally third gear it spikes at about 16 ish then levels a bit lower and feels right, then if I drop to fourth or fith and slow down and try to pull away again the boost shows 28psi. Also at higher speeds of about 70 it won't pull as the boost builds, then it over boosts again.

Would vag com throw up a high boost code? I haven't had any yet?


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## Stealth69 (Jun 25, 2012)

Hmmmm could be the n249 not doing its job then, that is supposed to prevent spikes or the n75 playing silly soda but you have already changed that to no avail, 5th&6th gear generate a lot of load on the engine when you thump your foot down which would cause the boost to generate quickly.

Don't think the ecu will chuck an overboost warning, if anything fuel cut should hit if it overboosts drastically, whatever has been changed doesn't sound particularly safe!


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## chrisTT-Norwich (Aug 15, 2012)

Hi guys and gals, I have finally fixed the problem! Thanks to all who helped me out. I made a turbo pressure tester using a wheelbarrow inner tube and instantly found a leak in the hose connected to the throttle body, I think it is the fuel pressure regulator, the braded hose had a bad end and the clamp had disappeared so re clamped and I'm now holding a solid 25psi and tapering off smoothly towards the red line. And it also fixed the rough idle too! :mrgreen:


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## t'mill (Jul 31, 2012)

You wouldn't happen to have a piccy of this offending hose in-situ would you?


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## chrisTT-Norwich (Aug 15, 2012)

I will take a picture later when I have my camera, but basically it's the small fabric braided hose that comes from under your throttle body and connects to the fuel pressure regulator which is a round metal valve sat right on top of the throttle body


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## t'mill (Jul 31, 2012)

If you could upload a pic later that would be marvellous. I need to sort out a similar issue with mine, so researching possible culprits on the forum reading folks posts.


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## chrisTT-Norwich (Aug 15, 2012)

Ok well in my limited experiemce I tried the following

I checked the waste gate actuator by making a small tube to pressurise the pipe and as the valve moved I knew it was ok
Second was the MAF try unplugging it to see if your engine improves, you will get a warning light come on but this will clear once MAF is plugged in again and you do a few short runs.
Third I checked the coil packs and plugs and measured the plug gap
Fourth I did a turbo leak test with a divice I made and instantly I found a small leak which cured everything!

Researching I have found that overboost problems usually stem from a leak in the turbo pipes making the wastegate actuator not open hence overboost, I will try and post some pictures with labels of the parts I checked and where I found the leak.

What exact symptoms are you seeing?


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## GPT TT (Mar 18, 2012)

I roughly have the same symptoms as your Chris, seem to be boosting 24-25 ish, them usually when in 4th it shudders and the boost gauge follows large boosts flickering.


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## chrisTT-Norwich (Aug 15, 2012)

So after 2 weeks or so of tinkering i still have not fixed the problem.

I have today done some more testing and have found something interesting. if i pull away on a nice straight bit of road, from 1st gear i can go all the way through to 6th gear and turbo is holding 20 psi then if i slow down and select 4th 5th or 6th i get the stutter and then overboosting to 27 psi and the engine warning throws up a Mass airflow error to mach air, any thoughts?

So far i have......
replaced coil packs and plugs gaped to 0.28
replaced n75
tried all 3 springs in my DV008 and even tried the stock DV
i have removed all charge pipes and tightened clamps
tested the WG actuator

I have noticed that when the problem occurs i can hear a hissing at the passengers side if i dump the gas a few times in quick succession it stops and starts then i slow down to 2nd or third and the noise goes and the car rockets!

If i cant solve this soon i may have to take it in to a garage but im dammed if im going to let it go this easily!

Please help me!


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## badger5 (Apr 19, 2003)

chrisTT-Norwich said:


> He told me he got a tuner near peterbourgh to do it, what I don't understand is the car was driving really well a month ago and not maxing out the boost but now it has changed, can't seem to find the problem. It seems that in 1st and second and occasionally third gear it spikes at about 16 ish then levels a bit lower and feels right, then if I drop to fourth or fith and slow down and try to pull away again the boost shows 28psi. Also at higher speeds of about 70 it won't pull as the boost builds, then it over boosts again.
> 
> Would vag com throw up a high boost code? I haven't had any yet?


that would be jabba I guess in that area
expect it to be a spikey map. with high initial boost spike on high load requests (4/5/6th gear)
mods done post mapping may have tipped the balance..

get it remapped again to suit what you have on there..


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## chrisTT-Norwich (Aug 15, 2012)

Just a quick update, I have now found three leaks under my intake manifold, the first is the pipe that connects to the fuel pressure regulator and the second in the vacuum pump and the third a pipe that comes off the vacuum pump, so fingers crossed when I get my new parts tomorrow all will be fixed


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## jamman (May 6, 2002)

chrisTT-Norwich said:


> Just a quick update, I have now found three leaks under my intake manifold, the first is the pipe that connects to the fuel pressure regulator and the second in the vacuum pump and the third a pipe that comes off the vacuum pump, so fingers crossed when I get my new parts tomorrow all will be fixed


Good luck with it mate I would also listen to what Bill had to say on the matter


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## chrisTT-Norwich (Aug 15, 2012)

All fixed and she runs like a good un


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## HawaiianTT (Jan 27, 2013)

hello there ladies and gents, new guy on the block here and chris it sounds as though i have a similar problem to you but not quite, 1st-4th (depending on how heavy i am on the gas) i get a max of 17 psi, then my engine hits limp mode, my friends vagcom reader picked up a mass overflow on the maf and an overboost condition, i replaced plugs and coil pack set the gap to 0.28, replaced the N75 and even slapped in a cold air intake and forge 007 dv currently using the yellow spring, anyone have any thoughts on my next move?


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## toocool (Nov 6, 2012)

if vag showed maf sensor does this not mean your maf has had it?


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## HawaiianTT (Jan 27, 2013)

Does it? I don't know anything, I mean I'm learning, but it's tough. Is that what it's trying to tell me when it says mass overflow? And would that cause a limp mode condition?


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## toocool (Nov 6, 2012)

I won't pretent to know much more but maf stands for mas air flow I think it's the sensor which goes wrong on them, as far as I know the maf measures the air flow going into the engine and adjusts fuel mixture and boost accordingly, I guess it could well cause it to go in limp mode if the sensors gone wrong and is telling the ecu theres very little air going through yet your foot is accelerating at 4k revs then guess the ecu just says this isn't right = limp mode. I could well be wrong but maf sensors and n75 valves seem to cause a lot of the troubles so worth checking, it would be what I would get checked first


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## thebluemax (Oct 11, 2012)

I would like to remap mine but there are so many stories about problems after the procedure that I probably won't have it done, unless I get WAK to do it, and boy is he good but he aint cheap!


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## HawaiianTT (Jan 27, 2013)

thank you toocool, ill get it checked out and replaced and post on here with the results, hopefully it fixes the problem, im so tired of getting beat by everyone, my car should be faster than that


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