Idle erratic

Tiny
MISSE0813
  • MEMBER
  • 2006 JEEP CHEROKEE
So here's the story. This afternoon, while driving the Jeep (Grand Cherokee Laredo), the sunroof opened without pressing any buttons. I closed sunroof and the problem happened again. A few minutes later, the instrument panel went haywire, multiple check lights were coming on and going back off. The RPM and Speedometer going up and down in sync intermittently - neither actually working. Headlights were flashing on and off (turned OFF), windshield wipers were not working. The hazard lights will turn on (but the instrument panel doesn't display the flashing lights at all or displays a solid green arrow to one side or the other), and the hazard lights will not turn off unless car is turned off for a little while. I pulled into a parking lot and put car in park and engine stalled (this only happened at this one time - car seemed to be losing power). I was able to drive the car home - the engine stopped stalling in park, but every other problem remained. I did some reading and found it could be the battery - so I had it checked at autozone, and replaced it. I did have a clogged sunroof several months ago that caused some water to leak into the car. Through the side panel at the top, but I fixed the clog and have had no issues since with clogging or water inside. I have had intermittent dash lights/warnings on in the past, but they have disappeared almost as soon as they appeared. My guess is the problem must have been there and just fully manifested this afternoon. Have you heard of this issue before!
Sunday, February 7th, 2010 AT 6:37 PM

20 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,738 POSTS
Wow! You do need a priest and not a mechanic. Just be thankful that you don't live here. We have near 3 feet of snow and it was 2 degrees this morning. Not exactly sunroof weather.

Now on to your problem. When this many things go bad, it usually is coming from a control module or computer. With your issues, I would start by having the body control module (BCM) tested. It controls a lot of what you described.

Let me know what you find. Also, my uncle is a priest, so if you need him. (LOL)

Joe
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Monday, February 8th, 2010 AT 8:17 PM
Tiny
DAVID KEMP
  • MEMBER
  • 1 POST
  • 2002 JEEP CHEROKEE
  • V8
  • 4WD
  • AUTOMATIC
  • 125,000 MILES
My 2002 Jeep has 125,000 miles and runs very well but on occasion the engine will not idle smooth for a few day to a few weeks. When in neutral the engine rpm will go up to 2,000 and then back down to 700 every 5 to 7 seconds. Is this something I can easily fix myself?
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the idle air control motor and the PCV and EGR valve also the throttle position sensor
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+1
Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
THICK650
  • MEMBER
  • 2 POSTS
  • 2000 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 139,000 MILES
Lately my Cherokee has been getting worse and worse gas mileage and when in park or at a stop light the idle is strange. It'll will sit at normal idle for awhile and then I'll hear a click and it will rev up for about 3 seconds and then go back down. I replaced the TPS and was going to look at the IAC or MAP but thought I would ask for recommendations here first. I have to take it down to Missouri and back to Wisconsin quite a few times this year for Army business so I'd like to get this problem fixed fast. Thank you for your help in advance.
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Has it ever set a check engine light when doing this? For something to "click" then have the idle jump is odd. Is the a/c turned off when this happens? At that mileage you are due for a full tune up, that may help your mileage issue, not sure if the idle thing is related, may just be a coincidence. Is there any chance of locating the relay or whatever it is that is clicking? Is it under the dash or a loud click from under the hood?
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
THICK650
  • MEMBER
  • 2 POSTS
The check engine light has never come on. The sound is coming from under the hood. I've turned the heat off and have never run the AC. Another problem is that it doesn't do it all the time, so I can't take it into a mechanic unless its exhibiting the symptoms. As for the tune up, its gotten one at 100k. The plugs looks fine, gapped correctly with no bridging.
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
If the problem correlates with the noise, you are going to have to find the source of the noise. The A/C compressor is the only thing I can think of under the hood that would cause the idle to change, but since that has been ruled out. Does the idle ever get rough or does it stay smooth and just surge? Thinking sticky lifter perhaps.
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
JULIUS187
  • MEMBER
  • 2 POSTS
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 98,000 MILES
1999 jeep Cherokee 4.0. Doesn't idle when you start it. Have to feather gas pedal. When you take it out of neutral and drive, it idles and drives fine happens whenever you start jeep
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check and test the idle air control valve, EGR valve and throttle position sensor
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
JULIUS187
  • MEMBER
  • 2 POSTS
Idle control valve is it located on the throttle body. Throttle position sensor where is that located
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Throttle Position (TP) Sensor (4.0L)On throttle body assembly.
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
JUDE123T676
  • MEMBER
  • 2 POSTS
  • 1999 JEEP CHEROKEE
Engine Mechanical problem
1999 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 70.000 miles

when I turn the key to start the engine, it won't turn over unless I give it some gas and it won't stay running unless I keep my foot on the gas for about 10 minutes or so, gradually letting up on the gas pedal until it idles by its self, then it runs fine. If I shut it off and restart it it's fine. It has new plugs and ais part. Whats the problem?
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,738 POSTS
Have you checked for vacuum leaks? Also, has the check engine light come on?

Let me know.

Joe
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
JUDE123T676
  • MEMBER
  • 2 POSTS
Joe, The engine light doesn't come on, this afternoon I went to start it and it was fine. Go figure
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
RAWMEAT
  • MEMBER
  • 1 POST
  • 1999 JEEP CHEROKEE
  • V8
  • AWD
  • AUTOMATIC
  • 100,000 MILES
When I start up it takes a few seconds to turn over, once running it seems to be idling at the lowest possible rpm, just staying alive. When I hit the gas nothing happens. The other day I started up no problem and drove for fifty feet then the accelerator stopped working and I slowly rolled to the side. It kept the idle but I couldent move. Started up again and drove, no problem. I think it is not cheap fix, I hope you can tell me otherwise. Thanks
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Friday, May 3rd, 2019 AT 1:58 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Clean out the idle air control valve and test the throttle position and manifold absolute pressure sensor
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Friday, May 3rd, 2019 AT 1:59 PM (Merged)
Tiny
ROCKET1LF
  • MEMBER
  • 2 POSTS
  • 1999 JEEP CHEROKEE
I have a 99 Jeep Grand Cherokee with the 4.7 V8 with 80,000 miles.
It has a problem with the idle oscillating up and down a few hundred rpm when it's cold or hot. Sometimes when I stop at a light the transmission will hold a higher gear for a few seconds after I stop and then I can hear and feel the transmission kick down. There are no codes when I plug in an Auto XRay 5000 scanner.

The engine and transmission have been serviced regulary

Could this be an idle control valve going bad or something else?

Any suggestions will be highly appreciated.

Thx Rick :roll:
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Friday, May 3rd, 2019 AT 1:59 PM (Merged)
Tiny
ROCKET1LF
  • MEMBER
  • 2 POSTS
I assume this is the transmission position sensor. Would this cause the idle to go up and down if the Jeep is in park or drive? It does it in both.
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Friday, May 3rd, 2019 AT 1:59 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
What TPS is, it's the throttle position sensor, and it is a possiblity, so is the IAC and the TCM tranny control module, tho unlikly would be more likly to thow a code than borderline IAC and TPS!
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Friday, May 3rd, 2019 AT 1:59 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Yes as far as the TPS goes problem is if it's hasn't thrown a code, The test on voltage mean little. Physical inspection after removing them will tell more, like plastic shavings and binding in the TPS, and as for the IAC real no test other than exchange! If it's idle issues only go with the IAC first!
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Friday, May 3rd, 2019 AT 1:59 PM (Merged)

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