I have a really annoying problem. I bought a 1990 Chevy C1500 2 wheel drive with the V8 350 in it. When I bought it from the guy, he explained to me that the guy he bought it from had replaced or rebuilt the engine. Now I have bought a Chilton manual for it and I've been looking at that trying to diagnose what's wrong with it. When I bought it, he told me that the truck would fire but wouldn't idle properly. Now I've replaced the idle air control valve, the throttle position sensor and I just put a brand new serpentine belt because I noticed today the belt was routed wrong and when I tried to rout it right, I found out the belt was too short. i also replaced the ignition coil and that didnt help at all. i was thinking about replacing the engine temp sensor because when i try to start the truck, the temp gauge in the dash goes all the way too 260+ and stays there while trying to start. but i talked to a friend of mine from carquest and he said that wouldnt stop the engine from starting so i am hoping to be able to pick your guys' brains and find out whats wrong with it.

 

For starters, you have some serious electrical issues going on; the ecm isn't at the same ground as the rest of the truck.

Check and clean all body and engine grounds. Look behind the right head; there should be a ground strap attached.

Allan

 

What makes you say electrical issues? I talked to the guy who replaced the engine and he said he also replaced the whole wiring harness and the old one was included when I bought it. I noticed a ground strap on the front of the engine and I looked at it but it looks fine. I've also noticed when I try to start the engine, the injectors and spraying alot of fuel out. Now I was told they shouldn't be spraying that much at start up..

 

Not an expert on the GM ECU, but most use the temp sensor input to set mixture. If the system thinks it's hot, seems it would provide less fuel at startup, not more. Does the needle go back to cold after you start the truck? Does it sit about in the middle when up to temp?