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HELP! My Jeep likes to die in the middle of driving

Ok, this is the short short version of a long drawn out story:

I have a 1997 Jeep Grand Cherokee Loredo Straight 6 4x4. I bought it because the engine is (supposedly) indestructable, in March 2010.

2 days after I pick up the car, the check engine light comes on. Codes read misfire in cylinders 2 and 6.

We do a complete tune up. No change; turns out the rotor was bad, so we replaced them again. That seemed to help…for a short time. Then the check engine light came on again, and despite changing numerous other components, would not turn off. Its been on and flashing periodically since last June. The codes now read misfire in all cylinders.

A few weeks later (after our initial tune up), the car would start to act like it was running out of gas, and would stall intermittently under all conditions: idling, accelerating, stopping, coasting. Our first thought was that the fuel pump was bad, so we replaced that. Everything was ok for a little while…

But then it would act up again. We replaced the coil, the hall effect device, cap, rotor, plugs, wires, entire distributor, hoses, belt, map sensor, maf sensor, idle control motor, cleaned the intake, replaced two screws that hold the computer cover on with shorter screws, cleaned all of the computer contacts, replaced the battery and cables, thermostat, new differential fluid, brakes, shocks, rear hatch lift cylinders and glass lift cylindars, heater motor, rear differential gasket/fluid, new radiator fluid, 5 bulbs and the third brake light…

I finally said enough is enough, after about $1500 worth of parts, we just succomed to the fact that our car would stop running randomly. When it would start to stall, giving it a lot of gas would seem to “clear out” the stall, and get it to run ok for a while. When it actually stalled, sometimes it would start again right away, and sometimes I would have to let it sit, and give it a lot of gas to start it.

This problem is very intermittent.

For a while, it seemed to be related to dampness or rain…but then it wasn’t. It would do it on sunny days as well as rainy days. But all the way from mid Novemeber through the end of February (it was very cold and snowy here in CT), it NEVER acted up once. Now that its warming up, its acting crazier than ever.

Its recently started misfiring a lot more often, and a lot worse. It will sometimes sound like the 4th of July under the hood. Yesterday I was driving home, and for about 15 minutes, I must have been driving on 3 cyclinders because it was like I was Jed Clampett driving in my jalopy, farting and popping down Main Street. Then, it just cleared out, and drove fine.

Jeep forums say it could be a bad CPU, bad wiring, possibly one of the two O2 sensors (or both), I heard it could be a crack in the fly wheel casing near the cam shaft position sensor magnet, and someone recently suggested replacing the intake and exhaust manifold gasket (we’re doing this tomorrow, as the parts only cost about $20.)

Has anyone had this happen? I’m ready to push this off a cliff and sign a lease on a new Toyota. Unfortunately, we can’t afford that right now.

I am not bringing this to the mechanic, becuase the problem is VERY intermittent, and can neither predict nor create the issue.

You bought a 14-year-old vehicle because you thought the engine was “supposedly indestructible.”

Is that correct?

What about the rest of the vehicle? What about the electronics?

You’ve obviously poured money into this vehicle.


Is this a labor of love? If so, go ahead and spend more money.

The end result will be the same, but go ahead, spend more money.

Jed, Is That The 4.0L Engine ?

One thing to throw out here is a Chrysler TSB (Technical Service Bulletin - June / 98 ) that discusses “Malfunction Indicator Lamp (MIL) illuminated with either a Multiple Misfire or individual Cylinder(1-6) Misfire Diagnostic Trouble Code (DTC) recorded in the Powertrain Control Module?s (PCM) memory. The MIL illumination may be accompanied by engine vibration.

The TSB says if diagnostic procedures identify a possible engine mechanical problem then the fix is new “revised valve springs” followed by an elaborate (easy, but time consuming) decarbonization procedure using a Mopar Combustion Cleaner spray. I believe those springs can be installed without removing the cylinder head. I can’t say if your Jeep has had revised springs installed.

I’d get with a mechanic who could properly diagnose this problem. Throwing parts at it isn’t working. Have them look at this bulletin, too. You’ve spent so much on this thing now that you could consider a reputable Jeep dealer for diagnosis. In warmer weather it may be worth leaving the vehicle for a mechanic to drive until it acts up.