Hi Don, mark hoyt in ketchikan here. Need help please! I have been working on a friends 1998 7.4 GI and we are at the point of pulling each other's hair out. We have replaced every sender, sensor, and everything except the wiring harness and nothing helps. All new TPS, IAC motor, IAT, MAP, injectors, fuel pumps and lines, fuel pressure regulator, spark module, cap, rotor, plugs, plug wires. We even swapped the ECM from my engine and it made no difference. Compression checked out good. Base timing is correct.
It won't start without giving it lots of throttle (like happens when you over pump a carb and flood it).
Once you get it to start, you have to keep it around 2000 rpm for a minute or so just to get it to idle without dying, then when you try to open the throttle it starts to die unless you're really quick to catch it and occasionally pops through the intake. The IAC motor seems to be overdoing it too.
I have never been stumped on one of these GM MPI engines before, but I guess there's a first time for everything. Any ideas?
It won't start without giving it lots of throttle (like happens when you over pump a carb and flood it).
Once you get it to start, you have to keep it around 2000 rpm for a minute or so just to get it to idle without dying, then when you try to open the throttle it starts to die unless you're really quick to catch it and occasionally pops through the intake. The IAC motor seems to be overdoing it too.
I have never been stumped on one of these GM MPI engines before, but I guess there's a first time for everything. Any ideas?
