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Jeep Cherokee Grand Cherokee Engine and Performance Problems



  • jc00jc00 Posts: 2
    My wife's 2000 cherokee 4.0L just started experiencing the issue.

    Which is strange because a co-worker just had his 2002 cherokee 4.0L have the issue fixed. He went to a dealer. They replaced the sending unit. It was good for a couple of days... then back again. The dealer then replaced the pump at the tune of $450.00+. His issue has not returned in 2 weeks. He also never experienced the engine running rough when the issue occurred.

    My wife's vehicle on the other hand was really struggling to keep idling. So, not having alot of cash, I decided to tackle the oil pump.... it is Michigan... 30 degrees and snowing in April.. NICE! I have been under the vehicle so far for about 8 hours across 3 nights. If I had a lift it probably would have taken me maybe 2 hours to get to this point. I am ready to put the new pump in.

    That being said, if it gets to the pump replacement stage with you, I would suggest paying the extra $300 to have it done for you.

    I will update this when the pump is in to say if it fixed it or not.

    At any rate.... We never had the issue until the wife took the Jeep to a Valvoline quick change. The clown over filled the engine. I am guessing two quarts. This allows the oil to be aerated by the crank. Also, to be noted we had used a semi synthetic the oil change before. So, this oil change took us from semi synthetic back to plain oil.... maybe this could pay its part in root causing this issue...

    more details to follow....

  • rllewisrllewis Posts: 2
    My 1994 4.0 Jeep Grand Cherokee started running terrible (bucking and stalling). I replaced the crankshaft position sensor, and it ran fine...except that afterword it started bucking after about 20-30 minutes after starting. It runs rough like this for about a minute...then runs fine again. It has done this without fail, every day for the last 6 months.
    It never stalls, and always starts.
    When it starts bucking, it slows down to around 40 mph, not fun when you are on interstate. Giving it more gas results in more bucking. It is definitely temperature related, during cold weather it takes longer to manifest.
    I have checked the coolant & manifold temperature sensors, MAP sensor, camshaft position sensor, and fuel pressure. I have replaced the spark plugs, rotor, wires, and fuel filter.
    I only get this problem for 1 minute, then it's gone.

    The onset of the problem is gradual (15 seconds), and it clears up over a 15 second period as well.
  • cpb2cpb2 Posts: 6
    FIXED! Turns out that it was the upstream O2 sensor, even though no diagnostic codes were set. Local shop put 2 hrs labor into diagnosing it an nailed it first try! Have driven it a dozen times now with no problem whatsoever. Go for it and post confirmation!
  • tuggajbtuggajb Posts: 646
    be sure to prime pump or you will have the same prob you have now
    i just fill it with grease befor i put them on
  • I have an '05 with the same engine. I have 57,000 miles on mine and I've never had that problem. Nothing normal about that to me.
  • After I changed the PCM, all is well.The funny thing about this is the dealer ship was just as lost! Great information on Edmunds. For all who are out there with a jeep crank shaft sensor or cam sensor Problem. If after changing the sensor and you still have problems you may have to change your PCM;that fixed my problem. I didn't have any luck with having the PCM checked by the dealership. GOOD LUCK!
  • I have a 91 jeep Cherokee with the 4.0 HO it starts and idles fine then I put it in drive and after about 5 minutes of driving it will just stop running, when I stop I can crank it over and it wont start but if I turn the key off for a minute It will start and do the same thing as soon as I start to drive. Rarely when it dies and I stop the starter wont even work but the radio and lights work.
  • I have the same exact problem with my 1994 4.0 Jeep Grand Cherokee. Have you found a solution?
  • pgr40pgr40 Posts: 2
    My son just purchased a 2000 GCL 4.0L with 74K miles.
    While driving it home the temp gauge showed 240 degs.
    I checked it out and found that the fan relay is bad:
    AC engages, fan doesn't go on.
    Temp exceeds 210 deg., fan doesn't go on.
    Switched the 40 amp fuse in the PCM, fan doesn’t go on.
    Hot wired, fan goes on.
    Is the fan relay on a 2000 GCL 4.0L the same and in the same place as your 2003?
    If not do you know where it is located?
    NAPA part#?
  • 440jeep440jeep Posts: 12
    I have a friend who uses MMO and he swears by it. But my father is a die hard slick 50 guy. I was wondering about which to use in an engine I am building (all brand new parts). or is the MMO stuff just for lubing up older engines?
  • jc00jc00 Posts: 2
    Sorry it took so long to follow up on my post. I went on vacation : )

    I got the oil pump in. I still see some fluctuation in oil pressure. At start up idle is it at 50 - middle. As we get up to speed 40-80 it gets up to like 55-60. The after the engine is warm and we come to a stop, it drops to about 40-45. The engine is running smooth again, and all is well.

    And thank you (tuggajb) for the previous post letting me know to prime the pump. I flipped the pump upside down and poured oil through the pickup tube until it began to run out the top of the pump. Then I flipped the pump back over and stuck it in a clean pan of oil. I then covered one of the two holes on top of it with my thumb (you know which one because the gasket would normally cover it), and began twisting the pump shaft with my other hand. It immediately began spurting oil out the uncovered top hole. Primed and ready to go!

    Good luck to all others that experience this issue...

  • tuggajbtuggajb Posts: 646
    be sure to brake in the new engine before mmo or slick 50 at least 1000 miles so rings seat or you will have a oil burner
  • rllewisrllewis Posts: 2
    Yes. I was able to monitor the crankshaft position sensor output long enough to see the signal go bonkers when the 1 minute problem happened. I replaced the sensor (which was under warranty) and now it is fixed. So the whole time it was the part I originally replaced. What are the odds?

    The part costs about $70.
  • 1spwcman1spwcman Posts: 3
    96 grand cherokee, six cylender, 2wd. i have a problem with my auto during first 5 minutes of running. after warm everything works great. example: cold start, starts great. runs like a champ untill put in gear then it stall and is hard re start. sometimes this doesn't happen. instead it starts great as before, and act fine until for a short period 1 or 2 minutes or until first brakeing to stop period, then it stalls and dies requiring restart. it usuall star easy after that and then runs fine for length time until it has another cool down period. usually after an 8 hr or so period of being shutdown, it act up again. any ideas. i've already replaced plug wires, idle air contol valve fuel filter, checked all vacuum connections, checked and cleaned ccv/pcv. whats next.
  • antheilantheil Posts: 6
    I have a 94 cherokee sport with this same troubles, and yes I have replaced the crank sensor. Is my PCM in the same place as your 92?
  • antheilantheil Posts: 6
    How did you monitor the crank sensor output?
  • antheilantheil Posts: 6
    Is there a way to test the O2 sensor before replacing it?
  • antheilantheil Posts: 6
    I just put a new engine in my 94 Cherokee and in the process broke the wires on the crank sensor so I replaced it. It started fine and run well for about 20 minutes. I took it for a drive and almost didn’t get home! It started missing and backfiring, the more gas I give it the worse it is. It will sometimes idle fair and then just cut off. It seemed like lack of fuel. I changed the fuel filter, but no change, there is plenty of fuel at the injector fuel rail bleeder. I replaced the distributor because there was shaft wear, but still did not help. I am now guessing it is electrical/sensor/computer related, but without test equipment I am guessing and trading out parts, any ideas
  • cpb2cpb2 Posts: 6
    Nothing conclusive without using special diagnostic tools. My mechanic was able to monitor a parameter of the O2 sensor and found it "unstable", i.e. bouncing from value to value erratically rather than a single state change from one vale to another as expected.
  • cpb2cpb2 Posts: 6
    There might be something you can do once you remove it from the vehicle, but the effort it takes to create the conditions and measure the results probably exceeds the part cost. $63 at an auto parts store.
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