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1990 4.0L Cherokee Stalling and Bucking Problems

I have a 1990 4.0L Cherokee that is having stalling and bucking problems. While driving or coming to a stop the engine would stall, I would hear a slight puff sound and then smell fuel in the engine compartment. At other times, usually on acceleration, the engine would buck. I had the vehicle towed 3-4 times to a shop and they checked the fuel system, the fuel pump (it was bad and replaced), and the fuel system power cleaned.

I have had the fuel pump replaced, the CPS replaced, the fuel system (injectors cleaned), and had a rebuilt PCM put in. The intermittent stalling continued and the engine would "buck" on acceleration like I did not know how to drive a manual transmission vehicle. The PCM was taken out and the original replaced (The reason the PCM was replaced was that at times after the engine was turned off the fuel injectors kept firing.)

After reading a number of posts on this group, I cleaned the connections on both the Throttle Position Sensor (TPS) and the Input Air Sensor (IAS) on the throttle. Upon restarting the vehicle, the engine stopped stalling in my garage (Yes!) and I was able to drive it without it stalling out for about 5 miles. It did buck a little and a few times the RPM level dropped a little but did not stall. On the drive back home it did not buck at all and the RPM level stayed consistent even at stop lights.

I am hoping that the cleaning of the contacts on the TPS and IAS has solved the problem, but I fear that it might be the PCM unit (see note above).

Finally, after I had the Fuel Pump replaced, the fuel gauge stopped working, at times it does come back on for a second, (which leads me to think a short, or an electrical (ground) problem. Does the PCM have anything to do with the Fuel Gauge? Should I request the shop that replaced the fuel pump to fix the fuel sender or could this have occured separately.

Thanks in advanve for any help or suggestions.

Otherwise this has been a great vehicle and I do not want to give up on it! Any other suggestions would be greatly appreciated.

Reply to
ltkaknm
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You likely have found the trouble.

Yes, go after the bozo's who put the pump unit in. The gauge sender is part of the same unit.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Mike,

Thanks for your response. This morning when I drove to work, it was doing it again. The RPM was fluctuating and it stalled once, but I was able to start it rather quickly. I am wondering if I should purchase a new TPS and/or IAS from the dealer or try to get one from a local junkyard. Or I might clean the contacts a little better. Do you have any suggestions on what I should use to clean the contacts. I am also thinking of getting a PCM from the same jyard if I can find my year and manual tranny.

Thanks again for your help it is much appreciated,

Tim K

Mike Roma> You likely have found the trouble.

Reply to
ltkaknm

When our 88 acted like that, it turned out to be a rotted mesh ground strap from the engine head to the firewall. The Jeep would steal grounds from other routes and act up.

I use a spray contact cleaner on the TPS plug and socket. WD40 will also work fairly well, but the proper contact cleaner sold at electronic shops is the best.

You can take a multimeter and put it on resistance to measure the TPS with the engine off and the TPS unplugged. As you increase the throttle, the resistance should change smoothly. If it jumps around, the TPS is likely in need of an internal clean or replacement.

Mike

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Reply to
Mike Romain

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