Im just wondering, a friend said 750 rpm is what a car is suppose to idle at however my Jeep 98 GC 4.0 idle's exactly between the 2 little lines before the 1k rpm mark. Basicly it idles around 500-600rpm, when the engine is cold started its always around 700 but goes up and down a little. Then after its been driven it always stays at 500 rpm exactly in the middle of those 2 small lines and doesnt go up or down.

The only thing i notice with the RPM's being at around 500 rpm is the engine is a little shaky when its idle. If i step on the gas a tiny bit to up the rpm to around 700-800 its smooth, then when it drops back down to 500 the car is a little bit shakey. Like it doesnt rattle, you can feal the engine vibration tho. The engine also goes like this... Its hard to say it in writing but bear with me. It sounds like this at ide.... CHUG CHUG CHUG CHUG CHUG CHUUUUG CHUG CHUG CHUG CHUG CHUUUUG CHUG CHUG (note this chug is normal sounding however in between it will chuuUg longer and when it does that the car will vibrate more RPM doesnt change when it does that tho) Today when my mom was driving with me in the car when she parked the car it sounded like it was about to stall which is a first. Also on cold startup the Jeep takes 3 seconds to start, it will turn over choochoochoochoo vruuum. Then after its warmed up it starts choo vrumm normally.

I know i sound like an idiot making these words up but its the only way to explain it lol


The car did have a tuneup like a month ago, but that didnt change anything for the worse. I replaced the old spark plugs with Platinum Champion plugs i quadroople checked the .035 gap, i also replaced the ignition coil, distributor cap and the rotar, along with the air filter, oil filter and the oil. It did the longer startup before the tuneup btw so it was nothing i did, the only thing the tuneup did was the excelleration was increased 2x very noticable, and the gas mileage increased. It also drives much smoother.

 

the idle is low compared to what it should be. The RPMs should be around 750 rpms. I have the same problem and have thrown everything I can at it short of replacing the PCM (computer). And still have the low idle/stalling problem.

What year is it?

 

98 GC 6.0