I have researched so many hours on here that if I was paid by the hour I would just give up and buy a new car. That being said, my car is running lean. Verified by my LC1 Wideband which I have just done a free air calibration to. Lean as in 18-19:1 cruising! It started randomly last week and I have not done any mods, nor changed anything that would cause the issue. I also am throwing no codes, so I assume the PCM thinks everything is OK? My current setup has been running strong and stioch for over a year: Injen CAI, stage 2 tune w 2.8 pulley, Magnaflow, ZZP Header, Downpipe and high flow cat.

1. I have checked for air leaks; I checked manifold bolts, vacuum hoses, used ether (motor cold) to spray every possible leak area, I even used a stethoscope to try and find any leaks. No leaks

2. I cleaned the MAF, checked the air filter, cleaned the gunk out of the TB, reset the battery, checked plugs and gaps. All was good

3. Yesterday, I drove around while commanding Open Loop to see if this would help, no change. This is where it gets interesting; I added 15% more fuel to the open loop cells, loaded the tune and forced OL again, this changed nothing. I scaled the MAF (with LC1) and this changed nothing! (Yes, I turned of LTFT, CL, DFCO and reset the fuel trims) I don't know what over rides the MAF as far as fueling but the changes I made showed no improvements.

4. Today I put stock injectors, stock tune (minus the MAF scaling that was working for a year) and reset the battery and it still was lean!

I am really stumped with all this, the ONLY thing I can think of that is left to try is the 02 sensor. My question is what else aside from MAF, injectors, tune/scaling and 02 sensor will have so much control over the fuelling?

Thank you!

 

Wasn't the oxygen sensor either... How can I be lean yet throw no codes? Guess I should look at fuel filter/pump next....?

 

Regular fuel station? Possibly you got a load of gas that wasn't all gas. High alcohol content will make it way lean, think running E85 on a car not setup for it. Could have been a mix-up at the station.

Also, how are your fuel trims? It's possible your wideband failed.

 

Thank you for taking the time to respond! Yes, regular fueling station. When I ran VCM scanner last week they were really close to being spot on. Guess I should buy a new sensor for my LC1.

 

If trims are good then it's probably your sensor

 

OK, I'll see if I have a spare. Thank you

 

Having the same problem. I know I need a new tune but this is not tune related. Goes lean about high 16s and it just has no power. If I let off and get back on it runs fine. Wot runs great

 

Mine showed lean at idle and when I was off the gas. It got worse as time went on. Checked for vacuum leaks etc same as you. Turned out it was the start of my flex pipe going. Letting in extra air before the o2 sensor and making the car think it was lean. Once I put a new DP on trims were fine.