Alan Billingham

Car in question is a 86 iroc with the original 305 tpi removed and a 85 350 tpi installed. Is the ECM`S different??? Current service no is 1227165 amu. When the car started playing up it was at 1500 rpm at idle with the cooling fans running constantly. All sensors at the cooling side checked for grounding and operation etc, all ok. When ECM is still hooked up with car running, if you move the ECM from side to side or lightly shake it, the car either cuts out or runs as if it is a couple of cylinders down.. My friends 86 305 tpi has installed his ECM in mine for a trial and it seems to work fine. His service no is 16198259. So the final 3 questions are; 1. Is my ECM knackered,
2. Are the 350 & 305 different,
3. If they are different, what service no am I looking for.
ps. The car is an auto.
Cheers ALAN.........

Grim Reaper

The 305s and 350s use the same ECM. However, 1985s used a different ECM (and eprom) than 1986-1989. There is a lot more info on the later 165 ECM (86-89) and generally people prefer the the 1989 calibration ($6E) than the earlier years.

There are different eproms between 305s/350s and standards/automatics. But the ECM on Third Gens are the same provided they are the same year. Also, the SD Vettes used a different ECM than SD F-body cars.

Grim Reaper

I got your e-mail. The "259" is a replacement ECM for the "165" btw, but it works exactly as the 165.