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I have a 2011 C6 with a mild cam, headers, and tune. I have been chasing an issue with my LTFT, I have a lean condition and will get a check engine light occasionally, both bank 1 and 2 fluctuate from 15-22% at idle. The values drop slightly under load, approximately to 15% but still not in a great range. So I figured this ruled out a vacuum leak but I did a smoke test any ways and I could not find any visible leaks. I cleaned the MAF and its values seem to be reading correctly, and also switch it with an another with no change. I replaced the O2 sensors two months after having an issue with them reading 0 (The car only has short term O2 sensors, long term were removed with the tune/headers) . I have yet to check fuel pressure, injectors or if the O2 sensors came loose. Any other ideas to help out would be appreciated. In general the car runs great under throttle and other than a small fluctuation in the idle it runs fine. I just wanted to get this numbers issue sorted.
If LTFT’s DECREASE under load and the car runs better under load when engine vacuum is low you have a vacuum leak…what are ”the car has only short term O2 sensors and long terms removed” mean ??…have you checked your exhaust upstream of the front O2 sensors for a leak ??…when your MIL illuminates (P0171/0174) post your freeze frame data.
If LTFT’s DECREASE under load and the car runs better under load when engine vacuum is low you have a vacuum leak…what are ”short term O2 sensors and long terms removed” mean ??…have you checked your exhaust upstream of the front O2 sensors for a leak ??…when your MIL illuminates (P0171/0174) post your freeze frame data.
Yeah thanks, I’m just struggling to find where it is, if I was reading the smoke machine properly the gauge was reading a leak size of 0.040” but I figured this amount was minimal. Meant to say the down stream O2 sensors were removed and coded out. Any common locations where there’s a vacuum leak that’s not visible with smoke?
How do you have your smoke machine hooked up ???…If you have a shop vac hook the hose up to the exhaust side to blow the air out and use a soapy water solution to look for that exhaust leak…if you have some propane (I try not to use anything flammable) spray it around the engine while it’s running watching your fuel trims go negative…when fuel trims decrease you found the leak.
Can you get to a scanner to see what your tps percentage is? A vacuum leak will have a near closed Throttle blade at idle
I can, it is reading 12%. Another thing I didn’t mention was “command air fuel equivalence ratio” is 1 with the range 1-20. After the car sat for a while LTFT are around 10-13…. I didn’t change anything. Curious what yall thing is going on.
Chasing LTFT in the 20%
