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Jeep Cherokee Grand Cherokee Engine and Performance Problems



  • 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.
  • cpb2cpb2 Posts: 6
    Replace the upstream O2 sensor. This is nearly identical to my problem that the o2 Sensor resolved. I have a manual transmission, so I don't have the same load on the engine when I'm stopped.
  • tuggajbtuggajb Posts: 646
    pos crank sensor unplug replug see if changes prob
    if not disconect batt reconect after 5 min try again let know what happens
  • antheilantheil Posts: 6
    OK this is weird; I have been charging the battery for a few hours and it runs better – not completely, but better. Then the battery volts drop below 14 and it gets real ruff again??!! It measures 14.7 when it is running and 13.6 when it is off –so it must be charging?! Does any of this mean anything?

    Tuggajb, after it got ruff again, I did both things you said (one at a time) and no change. Does any of this higher battery voltage mean anything? 14.7 volts sounds high enough to think the alternator is working or does it? Could the electronics be this sensitive?

    I am charging again now and will leave it until tomorrow and I will try again
  • jeeptsijeeptsi Posts: 8
    My pcm is located on the passenger side firewall next to my coolant reservoir. you should see fhat looks like a small flat box with possibly 3 wire connections hooked up to it. :) I have a 97 jeep gc tsi. It should be in the same place.
  • tuggajbtuggajb Posts: 646
    Batt voltage of 13.6 not running seems high should only be 12.6or7 when off
    how old is batt?
    have you checked all ground straps? one at rear of engine from head?
    have you gat a nother batt that you can hookup temp? try that voltage is sentive on the jeeps
  • antheilantheil Posts: 6
    94 Cherokee more info –

    I discovered, I am measuring bat voltage immediately after coming off the charger – it settles down after 30 min or so. This is a rebuilt engine and all the ground straps are clean and tight.

    Sometimes it will idle just fine, and just cut off. When it is idling fine and I barely crack open the throttle it spits and sputters? Could that be the TPS? What is the other sensor next to the TPS? Sometimes it will smooth out and I can ease it around the block a few times, but if I get on it, it bogs out and goes back to spiting and sputtering.
    Thanks again
  • mrquazymrquazy Posts: 2
    I just bought the wife a 1 owner & very well taken care of 99' Jeep Grand Cherokee Laredo. It has the 4.7L V8 with 90k actual miles. Heres the problem:

    When its first started up in the morning, the oil psi is fine. The oil psi drops down to zero when accelerating and then goes back up to 40+psi when letting off the gas pedal. After its warmed up, it has excellent oil psi and never drops below 40? The motor sounds extremely healthy and never rattles or makes any wierd noises. It also has the correct amount of oil in it too. Anyone out there have this problem or know what is wrong? I am hoping its just the sending unit and not the pump? Thanks in advance!
  • tuggajbtuggajb Posts: 646
    i would check sender price and if not to much replace it first

    repair manual shoes that it sends single to pcm and that then sends sig to gauges and controls ingector out put

    i would get a manual gauge from pep boys autozone etc and hook it up and then get readings from there that will tell you if you want to change sending unit or if you have bad gage then you will know for sure that you have oil pressure and what it is for surecould be loose wire
  • I'm having the "classic" cherokee overheating problems. DH has replaced thermostat, water pump, lower rad. hose, and cooling fan. I overheated yesterday on our first warm day after sitting at a drive thru for maybe 3-4 minutes.
    So he hot-wired the cooling fan last night and it is not working. Have another one on the way. Could there be something making it "go bad?" Dh says he is going to direct wire the fan to a toggle switch, as he feels it does not run enough. Only comes on after it hits 210. ANy ideas? It's an 01 Cherokee Sport, with 129,000 on it. 40,000 when I bought it, and the overheating problems started at the end of last summer.
  • fixjeepfixjeep Posts: 7
    My info says the sub fan is supposed to come on at 223 f and shuts off at 217 f .the coolant temp sensor and the a/c high pressure switch are responsable for telling the pcm when to turn on the sub cooling fan, the pcm grounds the cooling fan relay.If it doesnt overheat on the freeway its problebly not a plugged radiator. . Check the fan clutch see if its pulling air through the radiator by holding a large piece of cloth in front of the grill and see if the mechnical fan is pulling the cloth inwards.
  • tuggajbtuggajb Posts: 646
    My bet says that you have a partley pluged rad
  • bs55bs55 Posts: 15
    Where is the oil pressure sensor? I want to buy a unit on ebay for 40 bucks and change it. My pressure has been up and down for the past year, going from 40 and dropping when idle but not to 0 but in the last month it drops after 5mins on the road when i take my foot off the gas and check engine lights comes on now, want to see if changes this fixes it.

    How much will the shop change me if i have them change it. If its a lot i'll try to do it myslef but where and how? Any help?
  • tuggajbtuggajb Posts: 646
    just above the oil filter at the front of engine
  • vrmvrm Posts: 308
    I am planning to buy a 2007 Grand Cherokee Laredo (3.7L engine).

    Should I be concerned about the oil pressure problem?

  • kikifkikif Posts: 1
    I'm having the exact same problem with the same make/model/year. Have you had any success? I just had an oil change, changed filter, etc...and check gages light for the oil pressure is still randomly coming on.
  • cheaponecheapone Posts: 2
    i have a 96 zj 4.0 i replaced the 4.0 with another of the same year. just cranks wont fire
    wirked fine b4 the blowup
    a garage said its my engine harness thats bad
    they sais if they pull and play w/it, it will start.
    i did this it still wont start,jujst cranks
    its driving me nuts
    please help
  • tuggajbtuggajb Posts: 646
    are you getting any spark (remove coil wire hold bout 1/4 inch from ground have someone crank engine to check

    if have spark then check if getting gas should be able to tell by pushing in little valve that looks like tire valve aut to have pressure there.

    could be crank sencer back by fly wheel on top of bell housing
  • billnickbillnick Posts: 10
    My wife has a 2001 Jeep Grand Cherokee with 10014 miles it just started to overheat, it was fine when going down the road but when she would stop the temp gauge went off the scale. Called the jeep dealer who stated it was a very common problem, and we could drop it off monday and it would be fixed sometime in the afternoon tuesday. They stated it was a fan relay. The Jeep book gave 8.5 hours for the change and the part is $75.00 ish, so a total repair of about $400.00 to $500.00 total (time and parts).
    To me this was alot of money for a relay switch, so I got a hold of a jeep repair manual and the repair started by stating that the bumper cover had to be removed, the grill, radiator, and head light assembly all had to be removed just to access the relay. Well I could see where the price came from. I did some checking and a friend had the same problem I had he took his jeep to the dealer, the repair man showed him to remove the passenger side head light assembly which is one torx screw and a 7mm head long bolt, the headlight comes out with a little tug and help of a med. screwdriver, the assembly pops out of several ball sockets and you rest it on the bumper, with the wires still attached. You then cut a 3" by 6" chunk of the plastic that the headlight sits on, I did mine with a cut off wheel, when I removed the chunk of plastic there was the fan relay, it was pop rivited to the inter-fender well, a quick drill of the pop rivits and a 4wire plug I had the fan relay in my hand. I paid the $75.00 bucks for the dealer part, (there is a aftermarket one) but I opted for the dealer part. The part came with 2 screws and 2 rivits I used the screws pluged it in and that was that. Replaced the headlight assembly, re-set the the check engine light and removed the high temp codes, I was done in about an hour and saved $400.00 in labor. When you cut the plastic I went right to the middle and made a hole so I could see the part and enlarged it so I could get my fingers and tools in. Jeep Part # 5017491-AB Relay PKG 8052328. I really hope this helps someone it is such a simple job, the worst part was the cutting of the plastic but start with a hole that you can see into and go to town. Bill
  • steverstever Posts: 52,683
    Great first post Bill - maybe you can turn that into a CarSpace Guide.

    Don't suppose you took any photos while you were cutting that chunk of plastic? ;)
  • billnickbillnick Posts: 10
    No but first thing in the AM I'll pop the headlight out and have a few ready for anyone that may need!!! Thanks for the reply...Bill
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