# Really rough Idle and air leak



## 9scottyp9 (Mar 28, 2013)

Hi Folks,

relatively new TT owner here, and overall a very happy chapy with it!! But.........

It has developed, in the last couple of days, a really rough idle, dropping to 500 revs and nearly stalling then jumping up to 1500 revs to compensate - if i dont give it some revs to pull away it delays for a second or two then kicks in really harshly, and on occasion will kangeroo hop in first or second when going up the rev range. 
At speed in 4,5 or 6th gear it feels ok, although the slightest of delays when putting my foot down before the power kicks in.

I did notice a few weeks ago a hissing sound coming from the engine and on investigation it was obviously coming form the fornt of the engine, but i couldnt locate a leak at all (i was looking for positive pressure leak and air escpaing but didnt think about a vacum type leak and air being sucked in) but ti didnt seem to be affecting performance.

I have done some trawling through the forums and th eMAF seems to be a common theme, so im investigating a replacement - does any oneany have other thoughts or tips to resolve the issue????

Thanks for your time everyone and hopefully i'll put some regular contributions to the site.

Scott


----------



## sallyday10 (May 22, 2012)

Hi Scott,

it's fairly easy to identify if it's a MAF problem or not. Disconnect the MAF wiring from the MAF itself - the wires plug-in. This will send 'no signal' to the ECU which will then revert back to a default air-flow level, adjusting the fuel mixture accordingly.

The car should drive reasonably well like this - if it does, then your MAF is faulty. If your symptoms of rough idle persist, then its more than likely not your MAF unit that is faulty.

Rough idles can be caused by many things, one of the more common on the TT is the PCV valve - have a search around as there are plenty of articles.

Hope this helps,

Mike.


----------



## 9scottyp9 (Mar 28, 2013)

Thanks Mike - I'll give it a go


----------



## sallyday10 (May 22, 2012)

Remember - leave the MAF in place - just disconnect the wiring plug - it should just pull off.


----------



## Wak (May 6, 2002)

Make sure the bottom of the TIP is securely connected to the Turbo.
Make sure the bottom of the throttle body pipe is securely connected to the MAP tube in front(lower) of the battery.

Dont be buying a MAF until you know for certain its not a hose off.


----------



## Jayne-Scotland (Mar 28, 2013)

Could it be ignition coil that requires replacing - Ignition coil can be located under engine cover.

Jayne


----------



## 9scottyp9 (Mar 28, 2013)

Thanks all - building myself a nice little list of checks!!


----------



## Wak (May 6, 2002)

9scottyp9 said:


> Thanks all - building myself a nice little list of checks!!


Do mine first ! :lol: 
could check the other charge pipe hose too but that rarer to blow off under the headlamp. Battery side more often.

If you pull the maf plug and it behaves it doesnt mean its the maf.

If all the hoses are sounds and no other obvious leaks then try a maf but you ideally need a leak test to be certain the charge system is sound and as mentioned check the TIP is on the turbo properly. no other hoses come adrift.


----------



## EscapeOfficer1 (Jul 19, 2010)

For a quick and cheap check - try using a length of hose pipe to your ear and 'fish' for the air leak with the other end.

I used to use a piece to balance twin carbs by listening to the difference in sucking sounds from the venturi and it worked fine.

If you have a leak, you'll find it in seconds...

EO


----------



## 9scottyp9 (Mar 28, 2013)

thanks EO

on the TIP front - any pictures to guide what and where i'm looking for issues?


----------



## 9scottyp9 (Mar 28, 2013)

Well coming out of work the easiest thing seemed to be to unplug the MAF, so I did that and Fired her up - the engine ran fine, and idle settled at around 750-800 revs and was pretty smooth 
The air leak is still there so needs little more investigation. 
Awaiting for a price for a new MAF


----------



## 9scottyp9 (Mar 28, 2013)

Been quoted 75 plus vat for a complete MAF or 30 plus vat for the sensor - gone for the sensor and coming tomorrow.

any tips on removing the sensor part? any special tools required?

(please excuse my lack of knowledge)

Scott


----------



## 9scottyp9 (Mar 28, 2013)

Update - new MAF sensor fitted, and its a million times better - but the idle is still hunting a little (know where near as bad tho)
A mate at work brought his vagcom in. plugged it in and there were 6 codes, but with no idea how old they were, so we re-set the codes, went for a blast round the block and re-plugged in - fault code 16487 came back up - intermittant MAF high signal. 
So, the way forward - as per my original post, i'm positive there's a leak in a hose somewhere, i just cant locate it at the moment - so i'm gonna get all the plastics off and have a good feel around and see what i can find. Also going to do a throttle body alignment using the vagcom to see if that improves things. Ideally should do a throttle body clean also, but not overly confident with this.

If anyone has any other hints or tips im listening

Scott


----------



## Wak (May 6, 2002)

9scottyp9 said:


> Update - new MAF sensor fitted, and its a million times better - but the idle is still hunting a little (know where near as bad tho)
> A mate at work brought his vagcom in. plugged it in and there were 6 codes, but with no idea how old they were, so we re-set the codes, went for a blast round the block and re-plugged in - fault code 16487 came back up - intermittant MAF high signal.
> So, the way forward - as per my original post, i'm positive there's a leak in a hose somewhere, i just cant locate it at the moment - so i'm gonna get all the plastics off and have a good feel around and see what i can find. Also going to do a throttle body alignment using the vagcom to see if that improves things. Ideally should do a throttle body clean also, but not overly confident with this.
> 
> ...


I've never seen a genuine Bosch maf sensor available as a sensor only change........ now you have a leak to find and are running a car on a cheap aftermarket sensor that is one of the most important input sensors to the engine management.


----------



## 9scottyp9 (Mar 28, 2013)

Hi Wak, yeah your right, its not a Bosch, ive got the part through a mate and didn't realise being a rooky! - as and when this bites the dust I'll upgrade to a bosch unit - it has got me into a better place tho
I've had the throttle body off for a look see today and discoved its pretty mucky on the inlet manifold side - so with some IPA and cloths nicked from work given it a dam good clean - i couldnt get right in to where the butterfly meets the body and didnt want to move the valve manually for fear of damage - can i move the butterfly or do i just try and get in as best i can????????
Anyway on rebuild and throttle re-set the car throttle response felt much better and 'fresher'!! so better. i also took the chance to get all the plastics off and have a root around to find the leak - i did track it down to the intersection where 3 small hoses come together underneath the inlet manifold - i did have a fiddle and waggle and the leak seemed to improve dramatically, but i can believe a waggle has fixed the problem - with its postion i couldnt get in for a reallt good look, so any advice on this one would be brilliant???????????
Enjoying my tinkering so far and seem to be making improvements, so thanks for all the advise so far
Scott


----------

