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Help with rough idle and acceleration - TIA

2004 Jeep Grand Cherokee Limited Inline 6 Cylinder Engine Automatic Transmission Stock - No modifications

Symptoms: After car warms up (3-5 Minutes) the engine idle drops to about 600RPM and the car starts shaking rapidly. When you accelerate the car shakes repeatedly between 600RPM and 1500RPM. At 50 miles an hour, pressing the accelerator slightly to maintain a steady velocity (which is about 1500RPM) the car will experience the shake while driving. Moderate acceleration the problem goes away. Lifting off of the gas and the problem goes away until the above rpm range is reached and then problem comes back

Followup: Computer diagnostics indicates a miss fire on cylinder # 5

Question: Could this be a clogged injector or are there other suggestions?

TIA Ken

Reply to
ken859
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Reply to
tim bur

Don't each of the coil packs handle 2 cylinders? Wouldn't both misfire?

Reply to
Billy Ray

Reply to
tim bur

They sure as hell do!

Reply to
bllsht

That's the 4.0L, not the V-8. 4.0L I-6 uses three coil packs, one per two plugs.

Reply to
Matt Macchiarolo

Reply to
bllsht

Reply to
tim bur

Only an open circuit would misfire both plugs on a lost-spark ignition... a fouled plug merely helps the other plug fire. __ Steve .

Reply to
Stephen Cowell

Reply to
bllsht

You said a failed coil would not kill 2 cylinders. It will, and that is what I was responding to.

Reply to
bllsht

Reply to
tim bur

Reply to
L.W.( ßill ) Hughes III

Would have looked similar to this Japanese:

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Reply to
L.W.( ßill ) Hughes III

Reply to
tim bur

The 3 coils dual-fire the spark plugs on cylinders

1?6, 2?5 and/or 3?4. When one cylinder is being fired

(on compression stroke), the spark to the opposite

cylinder is being wasted (on exhaust stroke).

(From page D-3 from CD Manual for 2000 WJ Ignition System Description and Operation)

Reply to
Billy Ray

Reply to
L.W.( ßill ) Hughes III

My point is that if you have a bad coil you will have 2 cylinders mis-firing.

Reply to
Billy Ray

Oh, so the waste spark system on the 4.0L different than the waste spark system on any other engine? Please explain.

Reply to
bllsht

Reply to
L.W.( ßill ) Hughes III

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