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2002 4.0l Grand Cherokee, rough idle, no codes

Discussion in 'Grand Cherokee, Durango, etc' started by Dustincoc, Nov 28, 2016.

  1. Dustincoc

    Dustincoc Member

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    I bought a 2002 Grand Cherokee Laredo and drove it home today. It's running really rough at idle(comes and goes, seems the longer it idles the worse it gets). No codes showing(per my cheap bluetooth code scanner). I am getting the 2 sets of 3 beeps when I start, which I believe indicates service is due.

    The battery was dead when I got it, sticker indicated a 2004 date so not suprising it wouldn't work. Jumped it so I was aware of the rough idle when I bought it.

    Previous owner had had problems with the fuel injectors needing cleaning. My brother who drives a nearly identical Grand Cherokee, and is a mechanic, said he thinks it's the coils. Also was told it has an evap. leak. The purge solenoid has already been replaced. I through a new gas cap on it first thing. In my drive back to the house, no check engine light so it hasn't detected a leak yet. Also when I got it, it has less than an 1/8th tank of gas and that had been in there since it was taken off the road in August.

    I'm planning on driving it into work in the morning as I need to put some miles on it to isolate the issues and hopefully set some sort of code so I know which way to head.

    Also have a bunch of suspension work to do(tie rods, ball joints, upper control arms, bushings in lower left control arm, sway bar links,) Has a supposed death wobble issue that I failed to replicate. I have found the upper control arm bushings are shot and also the upper tie rod end on the passengers side was wasted, could move it up and down 1/4". Some wiggle in the others but nothing that severe.

    Previous owner included new tie rod ends, ball joints, lower control arm bushings for the front left, new sway bar links all around, and (3) 4-packs of injector o-rings. I already replaces the totally trashed tie-rod end but didn't have time to get into the others.

    Parts purchase list for tomorrow is as follows so far:
    -Full tank of gas+B-12 Chemtool
    -(2) upper front control arms
    -Fuel filter
    -Oil & filter
     
    #1 Dustincoc, Nov 28, 2016
    Last edited: Nov 28, 2016
  2. valiant67

    valiant67 Rich Corinthian Leather
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    Probably a good time to pull the spark plugs and inspect them. Lots of pics online to see if it's rich, lean, oily in the cylinders.
     
  3. Dustincoc

    Dustincoc Member

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    Planning on replacing them so I picked up a set tonight. Ran out of daylight to change them. Was planning on taking a close look at them. I may go out and change them with a flashlight but I've got to figure out how to get the coils off.
     
  4. 12soldier

    12soldier Well-Known Member

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    Had the same problem in my old 89 Cherokee 4.0. It could be the TPS (throttle position sensor), oxygen sensor, or even the more expensive TPMS/main computer. Any number of problems could be the cause, but mine never gave a code either. I eventually bypassed the ignition system and installed an aftermarket high powered MDS like system. This worked for about 6 months and the problem returned. I eventually abandoned the fixing of it, joined the military and left it sitting for 6 years at my moms. Before I could get back and try to work on it again, Hurricane Katrina washed it away in her high waters. I still miss that Jeep, I especially like the little pop out windows because my a/c broke too.

    But yours sounds like it could have similar problems. Mine would stutter while sitting at red lights, sometimes surge to about 3,000 RPM while sitting still at idle, stumble on start ups and turn off again. I changed the TPS, the throttle body sensor, some vacuum tubes, the thermostat in the radiator, and used almost every chemical on the market at the time to try to clean out the intake and fuel systems, I even installed new fuel injectors, fuel pump, and fuel filter. None of that fixed it. So I was left with the oxygen sensor and the main computer as other possible solutions but couldn't get back to try that do to military obligations. I would check the computer/TPMS first if I were you. I hope this helps.


    P.S. I took it to the Jeep dealer about 5 times and they couldn't figure it out. Some said it was the transmission, like a sensor that detects which gear your in and adjusts the engine fuel and air mix to accommodate. But didn't get that checked either.
     
  5. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Not clear to me - did you replace the 12-yr old battery that you jumped? If not, this is likely the source of your troubles. That, and perhaps old fuel that needs to get purged. Ethanol fuels seem to go bad faster because they absorb water and moisture and it diffused throughout the fuel.
     
  6. Skinpine

    Skinpine Active Member

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    A worn out or broken motor mount will cause a rough feeling idle. As Bob said, fix the battery first.
     
  7. Motor

    Motor Member

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    Doesn't hurt to spray clean throttle body and plate well with Throttle body cleaner either.
     
    12soldier likes this.
  8. 12soldier

    12soldier Well-Known Member

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    Updates on the problem?
     
  9. ImperialCrown

    Level III Supporter

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    Your 1989 is a way different animal than a 2002. The '89 Cherokee is a Renix (Renault-Bendix) MPFI system which gives no fault codes and has no 'ck eng' light. The Jeep/Eagle adapter for the DRBII lets the technician go through a number of motions to run various tests to find the problem.
    I remember the AMC Jeep/Eagle merger with Chrysler and how the Jeep became gradually Chryslerized. A description of the old Renix system is given here:
    Renix diagnostic and some general info - Jeep Cherokee Forum (at https://www.cherokeeforum.com/f2/renix-diagnostic-some-general-info-152596/ )
    Renix wasn't a bad system, it was just that there was virtually no factory service support or service publications for the technicians and most technicians were totally unfamiliar with it.

    The 2002 is a Chrysler SBEC/NGC EFI system that has fault code capability. Not every problem will set a fault code and this is where one would need the diagnostic manual and appropriate tools:
    http://oskin.ru/pub/chrysler-dodge/manuals/Service Manuals/2002_WG_Jeep_Grand_Cherokee/02wgep.pdf

    There are other tests that can be run to find problems when no codes are present. It just takes the correct tools and skills. Basics such as Ignition, Fuel and Engine Mechanical systems must be healthy and ruled out first. See the No DTCs checks from p. 218-232.
     

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