I have a 2009 Chevy hhr 2.0 turbo. Cold the idle surges bad, Once into closed loop the idle jumps up to 1,400-1,500 rpms and wont come down. Fuel trims will be great one time, then the next time you start it, there at -30% with no changes to the ecm.... Did install a new mass air flow sensor. Still same results. suspect the ecm is going out,,,, But maybe i have missed something in the tune... Please let me know your thoughts? Or changes i should try?
I'll upload my tune and data log2009 chevy hhr mod tune36.hpthhr closed to open loop1.hpl