1990 Jeep Ignition Inigma

[shawnjohnson66]

I have a 1990 Jeep Cherokee 4.0, L6, Fuel Injected. I put a new engine in, replaced the computer, Ignition Module etc.. It starts real hard and runs rough, but if I hold the Coil wire about 1 inch from the coil and allow it to arc to the wire, the engine smooths out completely at all RPM's. If I move the wire closer, the engine gets rougher, if I move it farther away it stalls. I also replaced the coil and it made no difference. What the heck could cause this?????

The wires, cap and rotor are all new.

PLEASE HELP!!!

Shawn

[fredjacksonsan]

Arcing across the air provides resistance to the flow of electricity. Do you have the right plugs in it?

[shawnjohnson66]

Well, I got the plugs from Napa when I got the rest of the ignition parts, but it is certainly something to check. I thought about the resistance approach too, but I cannot figure out how to increase the resistance, I have used both high performance and stock wires, the plugs are something I haven't thought about, any suggestions on an approriate plug? I have NEVER ran accross a problem like this before!!!

[fredjacksonsan]

Yeah, the plugs shouldn't make THAT much of a difference. I had another thought...vacuum hoses. Your engine can run rough if they're not hooked up properly. Check all those, and also your intake and air filter.

Also make sure that your plug wires aren't crossed; I've had some vehicles that were sensitive to that.

[shawnjohnson66]

Hey Fred, I really appreciate the advice, I'm gonna try chasing the vacuum system, I also heard that the distributer being off a toothe may cause this as the arc could cause a retard in the timing. I'll repost a little later and let you know either way..

[fredjacksonsan]

Welcome. You're right - timing would also do it.