Hey everyone, New to the forum and trying help my uncle out. Hes been replacing so many parts on his truck and i decided to register him on this forum and help him possibly find the problem.

The truck is a 1993 chevy suburban 7.4l 454.

The truck starts and barely idles and sputters, put it in drive and it will not idle what so ever. When you actually try to accelerate it almost seems to go in limp mode and not allow you to accel above 2000 rpm. Also even if you do get it to idle the truck seems to run rich.

He has had the timing redone time and time again.

We unplugged the map sensor just for the hell of it and it runs alot better idling wise. So he assumed it was that and ordered it and there is no difference. Then he replaced his dist cap, rotor, plugs, FPR, injectors and just today his o2 sensor.

He just keeps buying more and more replacement parts with out finding the problem. I've helped him when i've had time but he doesnt want to even work on it. Soon as i even talk about a part that could be possibly bad he just buys it without any thought.

I've also done a compression test and its just under 150 PSI each cyl.



Im assuming its an electrical problem thats based on the fuel delivery system. But i cant really tell forsure.

Thoughts ?

Thanks !!

 

Idle air control valve? If your model year has one. Just a thought.

 

GMCjohn: Welcome to the forum.

Check fuel pressure, it sounds like a failed fuel pump.

 

My '95 350 was running about the same. I replaced the fuel filter and fuel pump and it runs great.