Neko
Pit Crew Chief
Sep 17, 2004, 6:13 PM
Post #1 of 1
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88 Jeep Cherokee Poor Idle
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Q: I have an ‘88 Jeep Cherokee with a 4.0l engine. At times, especially when warm, the engine starts hard and idles rough. Sometimes it will start right up no matter what the conditions are. Now when warm, the engine idles too high, approx. 1300 RPMs and feels as though one of the cylinders is misfiring. However, above idle and at cruising speed the engine does not hesitate or skip a beat. I'm suspecting a vacuum leak but cannot find one. Please help!
A: I would suggest checking the Exhaust Gas Recirculation (EGR) valve. The EGR valve introduces (feeds) exhaust gases back into the engine at the intake manifold. The reason for this is to reduce combustion temperatures. This, in turn, reduces exhaust emissions. The EGR valve is suppose to be closed at idle and opens at varying amounts while the vehicle’s being driven. A sticking or defective EGR valve can really mess-up the engine idle, causing erratic idle speeds and misfire or an engine skip that would lead one to believe there is some sort of vacuum leak. If inspection of the EGR valve finds that it is not sealing properly or is opening in an untimely manner a replacement will be needed.
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