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Jeep Cherokee Grand Cherokee Engine and Performance Problems



  • tidestertidester Posts: 10,110
    Please continue the cold air intake discussion here: hemified05, "Cold air Intake systems for HEMI" #1, 8 Aug 2007 5:00 pm

    tidester, host
    SUVs and Smart Shopper
  • tduff67tduff67 Posts: 1
    I put the K&N system on my 07 HEMI. It did add about .5 MPG but also made the intake very loud under throttle. I also switched to full synthetic oil and that added about 1 mpg. As for wet vs. dry filters, I have used K&N's wet filters on every vehicle I have owned for the last 10 years or so. You RARELY have to clean them and I have always got at least a little bump in power and mileage.
  • almgjkalmgjk Posts: 1
    i had the same problem, its the engine control computer. The ground feed to the fan control module is lost from the ecm when the a/c system is run for the about 30 minutes.
    $1000 plus diagnostic $180
  • pj95pj95 Posts: 1
    i have a 07 grand cherokee 4.7l v8 with 2000 miles and if i use regular gas i get little hesitations while accelarating when i used super it seemed to go away and in the manual it says 87 is fine to use is this a problem or is it normal.
  • 1993 Jeep cherokee overheating. Changed water pump, and fan clutch, did pressure check on ststem, put on a new head gasket. Still overheated, took out the thermostat, put it back together without one, changed the antifreeze solution to the water wetter and water. Still overheats. Will run at about 230 at 45 MPH, but turn on the air or go faster, temp climbs. Electric fan is running. HELP!!!!!!
  • tuggajbtuggajb Posts: 646
    rad proble is cause part pluged
  • thanks, i flushed it with the hose, guess I need to get it power flushed
  • It not the thermostat, or pump, Its the coolent level sensor in the overflow/resovor, should read 3300k ohms, the plug that goes into the back of the screen, under the radio,controls, has a picture of the viechal, tells when a door is open ect... the #1 terminal goes to the coolent level sensor, try cleaning the connector, that usually fixes it, if not sheck the wires. If it;s a light on dash...same.....
  • bfritzbfritz Posts: 1
    Over last 2 weeks my oil pressure has gone up to a point where it is on H when highway driving at 110 klms. Seems to be ok but am concerned and not near a service depot. Any suggestions or advice appreciated, hate to get stranded out in the sticks here.
    I am in Inner Mongolia and nearest service is about 20 hr, drive.
  • landj68landj68 Posts: 6
    My 94 JGC 4.0L quit while driving just like the key was turned off. I found no spark from coil, further testing showed no signal from PCM to the coil. I sent out my PCM to be repaired and when it came back I still had the same problem.

    I then took it to a shop and they said the PCM was defective. They replaced the PCM with a rebuilt unit and then the car would start and run but would not rev past 3,000 rpm at 3000rpm it would start sputering and backfiring. The shop said the Catalytic converter was clogged and they replaced it and told my wife that the car was repaired. She had to limp home with the car as it still has low power(must accelerate very slowly or engine bogs down)
    and still will not rev past 3,000rpm.

    I checked back pressure at O2 port is exhaust and there is none. I then checked the timing with a scanner and it shows 14 - 16 degrees advance at idle and increases to 40 degrees advance at 3,000rpm where it starts sputtering and backfiring. I then connected a timing light to check the timing at the crankshaft. It shows 0 degrees advance at idle and increases to 15 degrees advance at 3,000rpm.

    I told the shop owner that the PCM that they installed must be defective and that I would pay the difference to replace it with a new PCM from Jeep, but he says that there is something else wrong with the car and he will have to diagnose it with an additional charge of course.

    Thanks in advance for any thoughts.
  • tuggajbtuggajb Posts: 646
    prob is the senser that is in the distrubater
  • landj68landj68 Posts: 6
    Thanks for the suggestion. Got the sensor (camshaft position sensor)from Autozone this morning and replaced it but I still have the same problem.

    Any other suggestions?
  • tuggajbtuggajb Posts: 646
    throtal pos sencer or crank sencer would try tps first
  • landj68landj68 Posts: 6
    Well, I replaced the throttle position sensor and the crankshaft position sensor today and still no change. My friend tells me that the PCM is the only device that controls the timing and since the timing is WAY retarded it has to be the culprit, but that part is $275.00 since the shop that put this one in says they will not replace it because they don't think it is the problem.

    Apparently my friend is the only one that thinks the PCM is the problem so I'm leary of spending that money as the pile of good replaced parts gets higher.
  • We had this problem on our 93 Dodge Caravan. After a year of different mechanics, finally found someone who told us that after market cam sensors seat in to close to the cam. Try pulling it out just a dime thickness and see if that works. Good luck.
  • I've had a few overheating problems in my 00 JGC. Here's how to diagnose... Let the Jeep idle and watch the thermostat. At 190 degrees, the fan should turn on at low RPM. At 210+ the fan should go on high RPM. If that fails you'll need to trouble shoot the fan relay. The location can be found at My relay had a bad ground connection (rusted) and once a proper ground was established, the fan worked properly and no more overheating. The fan should turn on when the AC switched on. This is a good relay test if you don't want to wait for the temp to come up. Check the connector to the relay, mine had evidence of arcing and I replaced the connector. If the fan is running and you're still overheating, it's time to get the radiator looked at. 700 bucks for radiator at the dealer, online for under 200 and takes 1-2 hours to replace.

    The service manual says that at 25+ mph the airflow is enough to cool the engine. I have tested this by disconnecting the fan and with the radiator alone the temp will stay under 200 when driving 25+ mph. Once you'll over heat.

    Good luck.
  • The electic cooling fan should come on @ 190 degrees. The temp sensor needs to be working and it's located at the thermostat housing.

    The engine will always overheat when idling if the electric fan is not working.

    The cooling fan relay is under the right headlamp. It needs a really good ground connection to work. Take it off, scuff up the back and the fender where it connects to and ensure a good ground. Use an ohm meter to verify there's a good ground. Many relays have been replaced that were good. The new ones were just clean on the back side and had a better electrical ground connection.

    Test the relay by turning having someone turn the AC on with the hood open to see if the fan turns on about 1-2 seconds after the AC is turned on.

    The stock radiator will keep the engine cool at 25+ mph. If the fan is working and you're still overheating, then the water is not moving through the engine and radiator. Take the radiator cap off when cool and squeeze the lower radiator hose. You should get fluid to gurgle at the cap, if not the radiator could be clogged.

    A 10mm socket will take off the thermostat housing. A thermostat is 10 bucks. Change it for good measure and be sure to change the gasket as well. Use a razor to scrape off the old gasket material.

    If you're still overheating, the water pump could be bad. Prolonged overheating can mess up the impellers in the water pump.

    Start with the electric fan first though....
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