[brandonlray]

I have a 1995 Grand Cherokee, just rolled 200k, owned it since 120k. Ran perfect until a few weeks ago, I removed my K&N Air Filter to clean it, re-oil it. I noticed a little bit of carbon build up in the throttle body, and sprayed a small amount of carb cleaner, and wiped it away. However, I did not start it. I let it sit over night. The next morning, it seemed to be idling a little high, around 1k, normally 650-700. I also noticed that when I let off the gas, it seems to want to propel itself, as if I still have my foot on the gas. Around 40, if you let off the gas, it feels like it wants to jump back and forth. Come to a stop, if you put your foot on the gas with any force, it wants to die, then the RPMS suddenly recover and it moves; but there is severe hesitation. If you put it in neutral and tap the gas one time, the RPMS bounce more than once as if I'm tapping it over and over. What's so confusing is that the problem is random. Usually happens once a day, sometimes the whole day sometimes just once during the day. 80% of the time it runs perfect, and doesn't have an issue. So far, I've replaced idler air valve, TPS sensor, partially removed and cleaned the throttle body, cap and rotor, replaced spark plugs. I took it to the Jeep dealer yesterday, the could not get it to act up at all. I took the tech for a drive, tried to get it to do it again and nothing!!!!! 20 mins after leaving it started acting up. No check engine light, dealer scanned for codes and nothing! I took this video tonight it hopes that someone might have an idea on this!!! Here is the link http://youtu.be/SqSknJln1PQ any suggestions would be greatly appreciated!!!! Thanks!!!

[bigbill888]

I chased similar things around for the last month. Battery tested good with some high tech thing. Today I decided to just throw a battery at it, but tested it first with an old school load tester. Found battery was junk despite being only two years old. Long story short: Battery was under warranty, new one $8.50, all idle problems fixed.

[brandonlray]

I switched out the battery yesterday, nothing. Still doing the same thing. I feel like it acts like a vacuum leak, but the problem is random. If I had a vacuum leak, wouldn't it be happening all the time?

[lauderdalechad]

Sometimes the oil from the k&n filters will screw up the mass air flow sensor...try unplugging it and see it it changes anything, take it off and clean it too but be gentle while doin it

Edit:
Scratch that...brain fart lol. Possible fuel delivery issue maybe?

[freakinheep89]

Originally Posted by lauderdalechad

Sometimes the oil from the k&n filters will screw up the mass air flow sensor...try unplugging it and see it it changes anything, take it off and clean it too but be gentle while doin it

there is no mass air flow sensor on a ZJ.

I would completely remove the throttle body and clean it by hand, you may have so much build up that its causing the throttle plates to stick.

[hdrocknroll]

Originally Posted by freakinheep89

there is no mass air flow sensor on a ZJ.

I would completely remove the throttle body and clean it by hand, you may have so much build up that its causing the throttle plates to stick.

And take out the IAC and clean it

[brandonlray]

I replaced the IAC already. Changed the Air Temperature Control Sensor last night, no change. Currently removed the PCM, found a little corrosion. I'm cleaning it off, fingers crossed! Also considered the MAP, but was told by the Jeep dealer that they've never seen them fail without a check engine light. Anyone have one go bad without the check engine light? Sea Foaming tomorrow if this doesn't fix it. Open to any other ideas!

[brandonlray]

After cleaning the terminals in the PCM, no change. Could it have an intermittent vacuum leak?

[brandonlray]

Problem solved!!!! Finally malfunctioned while hooked up the computer during it's second trip to the dealer. Coolant Temp Sensor was the culprit. The technician said he had never seen a coolant temp sensor that failed at random like mine did. He said it was sending funky voltage signals to the ECU. I of course, took it home to change it, flushed the coolant while I was at it. FIXED FINALLY!! Runs like a top! Probably due to that, plus a new Idle Air Valve, TPS, Map Sensor, Sea-Foamed motor. None the less, Brent Ross and I are friends again.

[lauderdalechad]

Good deal! Thanks for letting us know what solved it!