Intermittent Problem With Rough Running Jeep

[Justin Graham]

'89 Jeep Cherokee, 4.0, auto., 2wd. I have been having a strange problem lately with my '89 XJ. On one occasion I was at a stoplight, it turned green and I eased on the gas, suddenly the Jeep began sputtering horribly, acting as if it were about to cut out. The more I stepped on the gas, the worse it sputtered. So I pulled off the side of the road, cut it off, cranked it back up and got the same problem. Eventually after 5 minutes of messing around with it the problem stopped and I was on my way. Even though the fuel filter and fuel pump have been replaced about 10,000 miles ago, I went ahead and replaced the fuel filter again then checked the pressure coming from the fuel pump. Two weeks later, and all of a sudden the problem comes up again while pulling out of a parking lot. After about a minute of tapping on the gas, it pulls out of it and is running fine. Then again today after work, I cranked it up and the same problem came up again. After about five minutes of sitting in the parking lot and tapping on the gas, it straightened out and ran good on the way home. What is going on here?? As I said earlier, the fuel pump has been replaced and its pressure is up to spec. Now the fuel filter has been replaced again. I searched and a came across the problem concerning fuel vapor in the #3 injector, but I don't think that is my problem since this has happened before the engine has had a chance to warm up. Any ideas and has anybody had a similar problem?

Thanks,
Justin

[Runnin'OnEmpty]

Ummm.....if you're sure the fuel pressure is OK, then I'd suspect a faulty TPS. They're easy to check with a multimeter; basically you're looking for a smooth voltage transition on the signal wire when the throttle is advanced.

The TPS is a variable resistor; chances are you have a dead spot in the lower range, where most of the wear occurs.....

[Justin Graham]

TPS was something that I had in mind. I did quick check on it by hooking up the mulitmeter, then slowly and gradually easing on the throttle while looking for any jumps or plateaus in the voltage. I didn't see anything unusual, but of course I did this test while the vehicle was running fine. Most of the time, the Jeep is running fine. Just on a few occasions the problem has come up. Could it be possible that the TPS is functioning fine most of the time, but on the few occasions that I mentioned it was malfunctioning? I'm tempted to just replace the TPS with a new one, but I don't like just throwing money at a problem without diagnosing it first.

Thanks,
Justin

[Runnin'OnEmpty]

Could it be possible that the TPS is functioning fine most of the time, but on the few occasions that I mentioned it was malfunctioning? I'm tempted to just replace the TPS with a new one, but I don't like just throwing money at a problem without diagnosing it first.

I agree, no sense in replacing a good part. You might try spraying the TPS down with WD-40 and see if that helps. Remove it and spray where the actuator arm fits into the housing. WD-40 won't conduct electricity, and it may smooth things out enough to see if the TPS is really at fault, since the trouble is so intermittant.....

[langer1]

Sounds like it time to clean all your electrical connections, try everything on the coil first and then the grounds.

[Justin Graham]

I'll give both ideas a try and see what happens. I'm a little weary about spraying WD40 near the TPS though. I've heard horror stories about people washing their engine compartment and ruining the TPS by getting it wet. I guess WD40 doesn't have the same affect as water on it?

Thanks,
Justin

[langer1]

I would not reccomend wd-40 for that either, if anything get electical control cleaner. WD-40 just gets to gummy and leaves a sticky film.