I am new here. I have a 99 Cherokee sport with a rough idle. It happens in park or at a stop light. The jeep shakes and shudders. The rpms go up and down slightly from about 725 to 775. I changed the IAC,TPS, new plugs (auto lite copper) new wires, cleaned throttle body, checked for vacuum leaks (none that I could find), new distributor cap and rotor. The only code I have is for fan relay. Changed that but code is still there. Jeep has 164000 miles. I hear a ticking that I can't really isolate Bc it pretty much only happens when I'm driving and the engine is under load like uphill or at lower speed. Don't know what else to check. Changed oil and tranny fluid. Any help would be appreciated.

 

You could try checking fuel pressure, long shot but you might have fuel delivery problems.

Another long shot, you might have a bad CPS.(camshaft position sensor different than crankshaft position sensor) It's located under the distributor and when mine started going out I had similar problems, engine would lose power and sputter, felt almost exactly like a fuel delivery problem. It's like a $15 part and should be easy to test.

Ticking isn't for older engines, might be related, might not.

 

Thank you facechase. I will check that out. I'm wondering if it could be a loose timing chain causing the valve timing to be off.

 

Try cleaning up the grounds in the engine bay. I know it sounds unrelated but a bad ground can cause some wonky symptoms.

 

I will give the cleaning a try. The engine is dirty so it can't hurt. Thanks

 

Is it loping like it has a big cam? Might be a bad O2 sensor. I have read that sometimes when they are out of spec but still working they might not set a code. Just a guess though. That's what mine was doing. Have the upstream unplugged temporarily until I buy one. Runs better just really rich and still idles lumpy

 

What it's doing is that it shakes then stops shaking then shakes again and it keeps going from shaking to not shaking over and over again at idle. I was thinking about the o2 sensor but when I didn't get a code I figured it wasn't that but maybe it is. Maybe I'll pull the upstream to see if it changes anything.

 

Well I replaced the camshaft position sensor but no change.

 

Hmmm. Well that's all I've got. One thing I recommend is to not just throw parts at it. Most sensors can be tested with a simple micrometer.

If there's one thing I've learned, jeeps really like brand new parts that don't fix anything.