misfire HELP!!

[dribz-s3]

hi,
Ive just got back from an early morning drive and whilst i was out the car started to feel like it was misfireing, so i got it home and put it on vag.com and there was no fault codes. it fells like its misfireing around 3000rpm and 5000rpm and with no fault codes i aint got a clue any help with this issue will be greatly appreciated
TOM
PS. car had oil, filter and plug change 5000 miles ago

 

[voorhees]

Its a bit ambiguous when you say it 'feels' like its misfiring,what is the car doing...is it actually missing or is it not boosting.

 

[dribz-s3]

well the car feels like its stuttering and i just assumed that it was misfireing and ive only got the shareware version of vag.com so not much info

 

[A3Tom]

Hmmm, sounds like it could be MAF issue. Mine used to feel like it was hesitating a bit when driving when the MAF was ********.

 

[IIIadidasboy]

Hmmm, sounds like it could be MAF issue. Mine used to feel like it was hesitating a bit when driving when the MAF was ********.

Could be, un-plug it and see if it goes away.

But it could also be electrical or fuel related. When you say plug change, do you mean oil plug or sparks?

 

[dribz-s3]

llladidiasboy: i ment the spark plugs (ngk iridium)also it dosent do it all the time just occasionally. if it was a buggerd maf would vag.com pick it up or do you just have to change it to find out?

 

[IIIadidasboy]

As you've changed the spark plugs, that hopefully means that you can rule them out. I've not had VAG-COM that long so I'm not sure if a simple fault code scan will show all MAF faults - I think that would depend on the actual fault - but you can confirm / eliminate the MAF by un-plugging it and going for a drive, if the problem persists then it's not the MAF, although I know you can use VC to log air flow so that might be useful to highlight MAF problems - might be worth posting the question in the VC section.

I've got a similar problem, I un-plugged the MAF and to begin with it didn't do it (thought I'd cracked it) but then unfortunately it started again, so now I'm thinking coil packs - or something else electrical. So I'm just going to systematically change the electrical components and if that doesn't work start looking again for air leaks (which are hard to find) or turn my attention to the fueling.

9/10 times a misfire is going to be fuel/air/spark related (remembering the "fire triangle" ) - hopefully it's not a compression issue.

 

[dribz-s3]

so just been and unplugged the maf and everything seems to be fine but does anybody know how long i can leave it unplugged befor thing start going wrong.
thanks to anyone who has helpped

 

[IIIadidasboy]

That means it's pointing to a problem with the MAF - which needs to be changed (Audi do an exchenge programme I believe at a cost of approx £80)

Not sure how long you can run un-plugged though

 

[dribz-s3]

so got back from work and unplugged the maf again and went out for a drive and the car is still doing it so is there a way of testing the coils?

 

[IIIadidasboy]

Not sure, I'm suspecting mine as well, so I would also be interested in this!!

Sounds like your problem is very similar to mine (thought is was MAF - and it came back to haunt me!! )

 

[abdus]

boost leak?

 

[dribz-s3]

ill have a look but ive just replaced the whole vacuum sysytem and ive got forge pipes on the boost system. Has anyone got the price of a maf as my local audi wanted 77 quid plus vat on exchange and that seemed a bit pricey to me

 

[S3 CYP]

dribz-s3,

Price from audi for MAF is about right, best get one from there rather than anywhere else. I has this problem and it turned out to be the N75 valve after replacing the MAF, coils, DV.