So my car's been sitting for about 2 months now while i tried to sort out some boost controller issues, and just havent had time to actually spend on it while i was consumed w/ some summer courses trying to wrap my degree up.

i took my car out the other night on low boost to check everything over, and the AFR's were about a full point too lean...around 13.0-13.2, while the AFR's were usually ~12.0-12.2..

can e85 that's been sitting in a gas tank for 2months be the cause for the sudden lean AFR's?

the car is filled basically to the top, so i got a full tank of gas to burn off before i can go refill and see if there's any changes, but i thought id ask in the meantime.

 

Not likely due to the E85 sitting. I'd guess the difference is simply due to weather differences - particularly temp and baro.

Read this thread:
https://www.evolutionm.net/forums/al...notes-afr.html

 

Ethanol is hygroscopic (likes water), so if left in open air, it will absorb moisture from air. As long you didn't leave the gas cap off, that wouldn't be an issue. Suspect its what Jim said.