Hi everyone I’m having a really annoying issue with my wife’s car. I had it at the dealership and to my shop at work 034motorsport and no one can seem to find out what is going on and I’m ripping my hair out not that I have much left anyway. So here is what is happening. The car runs like a champ when cold. but once it warms up cylinder 2 will misfire. We had ran compression checks that came back good. New plugs, new coils, new injectors, pressure tested the supercharger intercoolers, borescope the cylinder and it looks good. Does anyone have any ideas on what in the world this could be or if they have had this issue before. I really could use the help! Thanks everyone.
Looks like you covered most everything. Do you have Vagcom? I would see if one of the shops checked into how often the misfires were happening compared to the other cylinders in the measuring logs. Also check the fuel trims by cylinder. Maybe it isn’t misfiring when cold due to cold start fuel enrichment and then running lean when fuel enrichment is off when warmer?
So with the vagcom the missfire count is constant on cylinder 2 and close to none on the other cylinders. Fuel trim came back normal as well. i was thinking wiring harness or lifter maybe but didnt see anyone reporting those kind of issues on the s4 mostly on the a4
Yea, lifter doubtful but there have been people with wiring issues. I guess time to put the old Ohm meter to work checking for resistance.
So you can test a few things.
watch the 02 voltage and wait to see if the misfires come once the 02s come on line. Then once the misfires happen hit the clear codes function in the vag com and see if the misfires go away for a few min.
Lastly are they real misfires or just phantom misfires registering.
they are very real dang car sounds like a subaru. ill test the o2 voltage tomorrow.