A4 misfires been chasing for months
 

ok so i'v been chasing these misfires since i bought the car the misfires are mostly on cyl 4 , 3 and 2 rarely on 1. so far i replaced all the IC piping , some vac lines, breather tube , turbo intake tube , DV , plugs , coils , maf , cts , fuel filter , o2 sensor , ICM. what else could it be i'm thinking either the ecu or fuel injectors how would i test these.

edit: forgot to add i mostly get the misfires on the highway around 2k rpms and above it seems the audi forums aren't much help i miss my dsm people and having people at my house to help after i post haha

If it's a 1.8t your valve cover gasket may be bad leaking oil on the plugs.

it is a 1.8 but it has new gaskets no oil leaking

try switching the plugs around and seeing if the misfire follows. BTW, nobody helps more than DSM people!

its also possible that your injectors are clogged up. you don't have to take them out to clean them though, autozone or advance have fuel injector cleaners. small cheap things like that is what i'd try first. hope it helps

i tried the lucus cleaner also seafoam

spray around your intake manifold with carb cleaner,if the intake sucks it in and the car boggles around possibly intake gaskets.

when you changed the coils did you do all of them at once? also did you change the icm at the same time or later?

oh i forgot to add that i changed the intake mani gasket last week just to rule it out lol im running out of things to try. i changed the coils all at the same time and i changed icm later normally with the icm only cyl 2 will misfire but i wanted to rule it out anyway

did the car just recently have the timing belt changed? if so maybe they put the belt on a tooth off or two. or samething with the cam chain if the tensioner was just replaced. is the car tuned, if so what company is it tuned by? also what year is this 1.8t

or possibly a bad crank sensor? idk

Crank sensor would be prolonged crank,as it wouldnt be able to find DTC

Check out the suction jet pump. I just replaced it in my g/fs 1.8t Jetta. It was causing misfires on 1 and 3, when I thought it was surely bad coil packs.

What year? If it has power output stages that could be it. Swap them and see if it follows

SteveO@OpenRoadTuning.com

i had a similar issue with my s, after replacing close to everything, it ended up being the icm. i have new ones. but what i didnt do was put the correct thermal paste between the icm and the heat sink. that fixed everything. but i have heard of brand new icms being bad. but you don't have the luxury of switching them and seeing if the codes and misfires follow them. since you only have one. could try a volt meter, hope that helps. another thing is are you running stock IC's? if you are id check them for a leak, mine had a small leak on the plastic end tank. but it could be something as simple as that. or you have a boost leak somewhere else.

Get rid of the ICM. Get an 02+ wiring harness for the ignition, wire it in to the ECU harness. Run the coils with integrated igniters. They are 18$ each and the 2.0T ones spark hotter. Pin out is the same.

Check your existing harness for black wiring. The **** gets so hot it burns up inside and blackens, it gains resistance, you gain misfires. The only way to find it is to cut it, but if your insulation is discolored and starting to brittle, which it probably is then it is likely done inside from heat cycling.

Check for carbon buildup too, these motors run super dirty PCV systems. It is not uncommon to see -21/-22 in hg vacuum at idle once you free your rings up, and that carbon causes weird stutter issues since it:

1. absorbs fuel causing fluctuations in afr between burn cycles

2. gets hot and ignites the charge early

Injector o-rings, and plastic bungs that thread into the intake manifold.... The plastic dies over time and expands when hot causing boost/vacuum leaks. Tested cold, they seem ok.

Owner hasnt had this car in at least 8+months.