B5 A4 1.8T sport - HELP


Registered User
Sep 10, 2015
Reaction score
Hey guys looking for some help.

Had my b5 a couple of months now and this morning after driving fine yesterday has developed a problem.

The car drives absolutely fine until you accelerate past 2.5k rpm and then it harshly judders

I've recently replaced the air filter and unplugged the connections around the air box but I've checked them all and they are connected.

Any help with diagnosis?

Thanks, M
you need to scan it really , but at wild guess the maf sensor or ign amp , coils. . Have you serviced car recently oil, plugs filters etc? might be worth getting cheap fault code scanner off ebay may point you in the right dirrection.
After a visual check for split pipes under manifold You could buy 1 coil and swap it around till you find the faulty one if just one.
That was my fault when car bogged down after 2500 revs scan doesn't show misfire
If old plugs change them bkr6e £6 for 4 on ebay too
Yeh its one of those issues that can be hard to detect, the ECU will often not have any fault codes.

My car had a coil fault, but it drove fine at low boost, and only missfired at or near full throttle. Swapped the coil and that sorted it.

My parents car had a similar feeling fault, but it happened in a much more random fashion, at much smaller loads, and unlike mine, would clear if you really floored it and kept the foot down.

I spent too much time replacing the coils, amps, spark plugs and even doing a TFSI coil conversion on it trying to sort it out, swapped MAFs too, and after all that, noticed an oily smudge on a hose coming off the inlet and realised it was split right thru underneath. Fixed the hose and bingo the problem vanished.
Yeah. Mine had the same. Missfired only at full throttle/boost and it was coil.
I've got a diagnostics thing and plugged it it and it said boost pressure sensor. Got one today and went to fit it and couldn't find it anywhere. Apparently they weren't fitted pre 2000 so **** knows why it came up.

Anyway found a split pipe and it was
Messing up the boost.

Had to cable tie on til tomorrow as don't have a hose clip small enough.

Anyway appreciate the help guys cheers.
Yeah all serviced now. Air filter was the last thing to be changed.