Intermitted misfire under hard acceleration


Registered User
Jun 7, 2012
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My car is a 2007 S3 with only 61000km on the clock. I have an irritating
problem that leaves me and the dealers completely puzzled. When accelerating
hard, usually above 4000 rpm, the car seems to produce a short misfire or that
is what it feels like. Usually only 1 or 2 misfires during the hard
acceleration but then the car continuous to accelerate freely to the red line.
No traction control light flashing, no engine warning lights displayed. The
funny thing is this doesn't happen every time. Sometimes I can drive hard for a
week with no misfire, but then all of a sudden the misfire is produced.

The car has been at the dealer 3 times already to find the problem, but still
the problem persists. They have done:

No error codes reported by VAS
Diverter valve replaced with the newer type valve
Thrust sensor replaced
O-rings on the boost pipe was apparently replaced
The high pressure fuel pump was checked for wear and seems to be in good
working order
Fuel filter was replaced
Replaced clutch/pressure plate/release bearing

I use 95 RON fuel in the car, but sometimes use a quarter tank 93 RON when 95
is not available.

The maintenance plan is ending very soon and I would like to identify the
problem preferably before then.

Your help and advice will obviously be appreciated.
It sounds like they havent done enough! The dealers are sometimes the best place to go when you have a problem like this because they can cross diagnose i.e. get a like for like car side by side and start throwing parts at the faulty car. My car was not part of the "coil packs" campaign but after 63k miles I developed a slight misfire as well and ended up replacing all 4 coil packs and spark plugs et voila you'd think but sadly no... one of the spark plugs was not gapped correctly and it was forever causing problems. The moral of the story is never trust these "ready to fit" plugs and always double check the gap before you put them in. As a dealer you would think that they would check things like fuelling as well... did they? Check out my hard starting thread here for more ideas:

Get yourself VAG COM if you can and start messing around with measuring blocks etc. Its a fantastic tool to have and do some of your own diagnosing.