Salam everyone.. I'm having an issue with a car that i recently bought. It has an Audi 2.0 TFSI engine.
Exhaust is sputtering huge amount of carbon soot. When i checked the engine oil, it was as dark as you'd usually see in a diesel engine. Service history showed it was changed less than 3000kms ago. Spark plugs came out as black as somebody did a fresh Matte black finish job, one of them refused to fire and resulted in cylinder misfire.
All these symptoms apparently point out to a rich fuel mixture but the STFT is at 0% (fluctuating when i play with throttle) and the LTFT is stagnant at around -6% ( and doesn't change regardless of the driving condition).
Pre CAT AFR sensor is responsive but the post CAT sensor has a stable 0.4v output regardless of throttle position. I was wondering whether it's been hooked up with a simulator but i'll have to look into it. Seems like Post CAT O2 is unrelated to rich mixture issue as ECU uses AFR (Pre CAT) values to adjust fuel mixture.
I've also checked and confirmed that Fuel pressure is normal and injectors are not leaking. Air Filter is also new and no choking there..
on a side note, there's quite a bit of Turbo lag not sure whether its related. Any thoughts?
