Well after nearly a year and half dead in my garage, my 93 Jeep was resurrected thanks to Car Talk (another posting)! Replaced the crank position sensor, and now have reliable fuel pressure. It still was running very rough, so pulled the plugs (two fouled out completely), cap and rotor (both worn), and it seemed to run much better. Then ran into a hard start problem on a cold day – so replaced the intake manifold air temperature sensor, which SEEMED to fix that problem. But now am still having a cold start problem. I have to hold the gas pedal down a little ways to get the engine to start and then run at about 1200-1500 RPM. If I let off the gas pedal while the engine is still in open loop, the engine stalls/quits. Once the engine gets into closed loop, the engine runs and will restart smoothly with no pressure on the gas pedal. Any ideas on how to further troubleshoot this cold start problem?
The first thing to check is the Idle Air Control valve. No matter the engine temperature the IAC valve is what controls the engine idle. The fact that you can get the engine started and keep in running by manipulating the throttle while in the open loop mode points to a possible problem with the IAC valve.
Thanks! Got the method from the jeep forums, the IAC was all crusted with carbon. Cleaned it and the chamber it fits into, reassembled and the Jeep starts and runs like new! BTW I also replaced the spark plug wires and that seems to have fixed a bit of a misfire as well.