1998 Jeep Laredo rough idle

Tiny
ROYBILLSTROM
  • MEMBER
  • 1998 JEEP LAREDO
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Runs great for about 1 minute then suddenly very rough idle for about 3 minutes, then just as suddenly, back to normal. Remains normal until engine is shut off for a few minutes. Upon restart, cycle is repeated. Warm or cold makes no difference.
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Wednesday, September 9th, 2009 AT 2:13 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Has the check engine light come on? Also, have you checked the EGR to make sure it is working properly? It may be sticking and causing this. When you remove it, make sure to clean the carbon from it and the intake.

Let me know what you find.

Joe
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Wednesday, September 9th, 2009 AT 10:39 PM
Tiny
ROYBILLSTROM
  • MEMBER
Thanks Joe for your reply. Yes, the Check Engine light is on. This vehicle ('98) doesn't give flash codes and I don't have a scan tool. Also, I don't believe this model (4.0 L) has an EGR.
I think maybe the key to proper diagnosis of this problem is in taking into account the consistency of the symptoms. The engine always starts, runs, even drives perfectly for about the first minute. Then there is a period of very rough idle, or if driving, acting a bit like it's running out of fuel with sputtering, hesitating, backfiring and jerking forward when I try to compensate by steping on the pedal. This lasts about three minutes, and suddenly the engine runs perfectly again from then on. I can drive all over town without a hint of a problem all day--that is, until I shut off the motor for a few minutes to run into a store or something. Then on restart, the exact cycle repeats itself, one minute of running fine, followed by a few minutes of pretty well non-drivability, and then back to normal. A real puzzler.
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Thursday, September 10th, 2009 AT 7:38 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I feel it is EGR related; however, I've been wrong before. What I need you to do is take it to a nationally recognized parts store and have them scan the computer. If the light has been on, there should be a code stored in the computer that will allow us to better doagnose the problem.

Most nationally recognized parts stores will scan the computer for free, so there will be no money out of pocket for you.

Let me know what you find.
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Thursday, September 10th, 2009 AT 8:12 AM

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