I have an 87 IROC-Z. The car was originally a 305, had a rebuilt 350 (stock vin code 8) put in a few months ago. The injectors were upgraded to 22lb ones, replaced with correct Knock Sensor and ESC Module. The smog stuff was removed. The trans is stock automatic 700r4.
I also ordered a PROM from TPI PARTS and that was installed with the engine swap.
Car ran fine for about 800 miles, for the past 1000 it seems to be running lean, I think, stalling, running rough etc…its drivable but not much fun. The car thinks its running hot but it’s NOT. The Computer (when my mechanic hooks his diagnostic reader up to it) says the engine is over 300 degrees, even on start up. But the temperature is really ok on the engine, computer is confused I think. And I think it is causing it to run lean or maybe retarding the timing. My mechanic is stumped. Coolant Temp sensor has been replaced, and the cooling fans re-wired so they run properly.

 

maybe a new ecu? i'm right down the road maybe put my computer in your car real quick and fire it up. I have an old school scanner that works awesome with these cars. shoot pm!

 

can you verify which sensor was replaced?

one in the driver head goes to the gauge on the dash
one in the intake goes to the ECM
one in the pass side head controls one fan(ecm controls other)

its possible that the CTS that was replaced, if it was the one in the intake, is already bad, the replacements are hit and miss if it was bought from a part store

it could also be a bad ECM or a fault in the wiring


does the temp ever fluctuate on the scanner or does it stay the same through the entire run time?