Misfire Help!!

[Sohrob]

My s3 has suddenly developed what i can only describe as a misfire, if i build the revs very slow then it seem ok and revs pretty freely in neutral. The problem is if i want to accelerate or drive fairly quickly.

Power is lost and the car judders, i can also hear chattering as though i was backing on and off the throttle.

My technical knowledge is pretty much zero but there was a lot of talk of the standard diverter valves failing, could this cause it?

Or could it be something like the spark plugs or coild pack?

the car is a 2007/57 s3 with 25k, was serviced a while back at Audi and has been running fine.

I am using GIAC software and the Evoms so am in two minds weather or not to go straight to Audi or try a local garage and see if anything shows on a diagnostic check.

Any ideas or advice would be great so i can pass it on to the garage.

Thanks

 

[Khufu]

missing suggests coilpacks but I guess your best bet is to connect to a diagnosis lead to see what it says. Has the engine management light come on? Are these the same symptoms of fuel pump wear too?

 

[Jamiekip]

On our spec engines it usually comes back to injectors or spark plugs.
Sparkplugs - Denso Iridiums seem to be the cure
Injectors are a warranty job - do you still get the miss-fire issue on your standard map?

Personally I would put your stock intake back on and flash back to the stock map and book it in with your dealer ASAP. Pain in the ***, but not worth giving them any ammo.

Good luck

 

[dc240969]

Have a wee look here. http://www.audi-sport.net/vb/showthread.php?t=62475
l havent had a misfire since lve also just put denso iridium plugs in mine.

 

[S3Alex]

My s3 has suddenly developed what i can only describe as a misfire, if i build the revs very slow then it seem ok and revs pretty freely in neutral. The problem is if i want to accelerate or drive fairly quickly.

Power is lost and the car judders, i can also hear chattering as though i was backing on and off the throttle.

My technical knowledge is pretty much zero but there was a lot of talk of the standard diverter valves failing, could this cause it?

Or could it be something like the spark plugs or coild pack?

the car is a 2007/57 s3 with 25k, was serviced a while back at Audi and has been running fine.

I am using GIAC software and the Evoms so am in two minds weather or not to go straight to Audi or try a local garage and see if anything shows on a diagnostic check.

Any ideas or advice would be great so i can pass it on to the garage.

Thanks

Mine misfired at 6500rpm for a while after having the Revo Stage2 software installed,and after a session of datalogging,it was decided that we would try the coilpacks first(which weren't the problem),then the plugs(which also weren't the problem),and in desperation I had a go with a couple of packs of injector cleaner,as I knew the sort of reception I would get from my local dealer.

This seems to have done the trick if not removed it completely,and I am sure that a few thousand miles worth of cheap supermarket fuel was the culprit,so that was a lesson learned.

The coilpacks would be the first place to look,as this seems to be the most common fault,followed by the plugs,and leaving the most costly one till last.

 

[Sohrob]

Thanks guys, with the car being modded for round 10k miles or so i can only assume that something like the coils have failed or the plugs have worn out etc.

For the last 13k the car has only EVER drank v power do i doubt its down to crappy fuel.

Going to get a friend to hook it up to the diagnostics and see if that shows anything before putting it back to stock and trying Audi.

Thanks again.

 

[Jamiekip]

If your mate had VAGCOM run some data logging too, might help throw up the issue

 

[Sohrob]

Also most people seemed to get there misfire very high in the rev range, my car gets driven right upto the limiter daily with no probs. The misfire im experiencing can be from as low as 2000 rpm.

Not sure if he has vag com but they are able to reset service lights and run checks etc. Will this be the same?

 

[Flibble]

Had a misfire on mine just after I got it - diagnostics showed it was a faulty ignition coil, and sure enough one rusty coil replacement later it went away. I had the ECU light on though, so if you've not got that it seems less likely it's a coil failure.

 

[Jamiekip]

Also most people seemed to get there misfire very high in the rev range, my car gets driven right upto the limiter daily with no probs. The misfire im experiencing can be from as low as 2000 rpm.

Not sure if he has vag com but they are able to reset service lights and run checks etc. Will this be the same?

With an injector issue it's always there, only sometimes it's so minor you can't physically feel/hear it. Data logging may expose it though.
I'll be intereted to hear how they diagnose it... fingers crossed they nail it on the first for you.

 

[Sohrob]

Also had the car up at Awesome on the rollers 2 weeks ago and they didnt mention anything.

Hmmm the joys of a non standard car, if i hadnt touched it i would be straight down to Audi.

 

[Spin140]

Also had the car up at Awesome on the rollers 2 weeks ago and they didnt mention anything.

Hmmm the joys of a non standard car, if i hadnt touched it i would be straight down to Audi.

How very true but then you would be bored, got to be worth flashing abck to stock and see if the fault still occurs, if so take it back to AUDI.

Good luck

 

[mrgicm]

So what is a difference between a missfire and a fuel cut in terms of engine noise etc... ??

 

[Sohrob]

4 new coils,good as new

 

[emzino]

Is changing the coils a DIY job? Also, how much did it cost all in. I'm getting misfires from mine quite alot =/

 

[AuldReekie]

4 new coils,good as new

Seems the A3/S3 are susceptable to this. My engine management light came on the other day and Audi diagnosed sporadic misfire in two of the cylinders. It is booked in this Friday to have all the coil packs changed too. Warranty no arguement.

Glad you resolved it.

 

[Sohrob]

Out of pure lazyness i didnt even take the car to Audi and have it done under warranty, end up costing £170 for the coils and fitting.

Only needed one but i thought i may aswell do the lot.

 

[AuldReekie]

That's what Audi recommended too. If you have the problem with one or more, they will do the lot as subsequent failures are common.

Not bad price you got though mate.

 

[Flibble]

Is changing the coils a DIY job? Also, how much did it cost all in. I'm getting misfires from mine quite alot =/

When the bloke did mine it looked **** easy tbh - unplug, remove old coil, put new one in, reconnect.

 

[emzino]

Oh ok. Might have a go myself. Just need to get the coils then. I guess it's like changing spark plugs then