OK, so I finally got the engine back in and running in my GTA. T56, 350 TPI, mostly stock with bolt ons and some porting. I just finished swapping in fresh lifters, plugs and wires, roller rockers, timing, putting correct injectors in it (will end up with some new bosch ones when I get paid) etc... It's been interesting to get it to this point to say the least.

So I get it driving and almost immediately I notice it's temperamental when it's hot out. I've been having a few codes: MAF too high, CTS too low, ESC error are the recurring ones. I had a fluctuating coolant temp sensor so I swapped it for a known good one and it went -38 degrees on me. I checked my grounds at the engine and they are OK so I figured it was the ECM.

Changed my ECM. No change.

It acts like a bad ignition module when it's hot; it will sputter, run rich, hesitate, stumble and backfire with poor power and driveability. What I found odd was if I shut the engine off and immediately restart it, it will run fine for a few minutes before it does it again which makes me think twice about replacing a GM ignition module. Anyone see anything this odd before?

 

U check the IAT? Believe it shares the ground with CTS.

 

It does and I checked it. No dice. Also did a circuit integrity check. Checked out ok