rough idle 93 4.0

txstateMarcus · #1 02-09-2006, 03:46 PM

Ok jeep enthusiasts, I have a 93 GC 4.0 liter that idles really rough. When driving after about 1000 RPM It runs perfect. Everything checks out Map sensor, TPS, fuel pump, fuel filter etc. However I changed out the spark plugs and it ran great for about 4 days and then started acting up again. I have replaced wires, distributor cap and rotor. Any insight to this problem would be greatly appreciated.

Ron68 · #2 02-09-2006, 08:03 PM

Quote:

Originally Posted by txstateMarcus

Ok jeep enthusiasts, I have a 93 GC 4.0 liter that idles really rough. When driving after about 1000 RPM It runs perfect. Everything checks out Map sensor, TPS, fuel pump, fuel filter etc. However I changed out the spark plugs and it ran great for about 4 days and then started acting up again. I have replaced wires, distributor cap and rotor. Any insight to this problem would be greatly appreciated.

If it ran great for four days after the plug change, and it doesn't now, I would check the plugs again. You may have a bad one. I have seen some feedback here about plug brands, with some working better than others. Which brand did you install? Pull the plugs you installed and inspect them for signs of fouling that would indicate a bad plug. A bad plug will be more evident at idle rpm.

You might also check the IAC solenoid (Idle air control). It can affect your idle. Pull it from the throttle body and clean it and the seat where the pintle rests. They can sometimes get gummed up with carbon or fuel residue.

txstateMarcus · #3 02-10-2006, 07:16 PM

Thanks for the advice, I'll try all that you reccommended.

flykr2s · #4 03-06-2006, 09:47 AM

I have fought this problem for almost a year. I replaced every sensor possible on the car. I replaced all plug wires, dist cap, rotor, and everything else you can think of only to have the problem continue and it was worse in cold weather. Well I finally decided to replace the coil even though it checked out ok. That was the problem. Now my 93 JGC Laredo starts immediately and runs betterv than it has for years. Maybe I can get another 235K miles out of it. Tip of the day: REPLACE THE COIL.

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