96 Cherokee problem local shops can't fix...looking for direction

[mikeandkim]

I have a 96 Cherokee 4.0L with 240K miles that has given little trouble til now. My local mechanics are stumped and there are no codes stored showing the issue. The engine begins to "buck" at times especially when starting a small hill. Giving it more gas gets it going again but the problem continues. Happens whether the engine is cold or warmed up. They have replaced plugs, wires, cap, rotor, O2 sensor, fuel filter (which was the factory original original, fuel pressure was checked and found to be fine, compression check done and still close to new specs and a crankshaft sensor. The problem continues and the shop doesn't want to keep throwing parts on to see if it works. It has a new transmission from a year ago as well. Any thoughts or has anyone had this problem?

[rjh]

have they wrapped the injectors? i know there was a problem with one of them overheating, and insulating them makes it go away. reward_1000 could give more details...

[JeepN4kc]

My 4.0 XJ does some weird stuff sometimes when wheelin. If I'm on a sharp angle (up/down/off-camber) at start up it does this bucking - especially the initial idle. After a bit it smooths out but I have to gas it some and move out with the choppy throttle until it levels off. I assume it is fuel pump, check valve in the fuel line, fuel rail, or injector related.

[jagular7]

I've read people searching and searching for the cause of the issue for fueling idiocracys. The fuel lines are steel. They can rust from the inside. Fuel filter won't catch that. They either blow clean the fuel lines or replaced them totally and that appeared to fix the fueling issues. Same for diesels where the fuel lines run after the filter and into the block.

[spunebil]

Mè ole xjdid same thing every now and then, ususally on hills. I just ignored it as I figured it a xj thing ! ;)

[reward_1000]

It is not related to the injector heat like Rich said. That problem will usually only occur when hot after it has been sitting for a couple of minutes. Your problem does sound a little on the weird though. It sounds as if there is something that could be shorting out causing for it to skip a beat. Especially if only doing it on hills. Can you duplicate every time, or is it just a once in a while type of thing? It does not sound like something that would trip a code so it does make it harder to find. Do you have a tachometer on the car? If so what does it do when this happens? Does it drop all of the way to zero or does stay the course? do any other gauges, lights or things act up when the problem occurs? is it only at a certain speed up a hill? I know I ask a lot of questions but as you know with a problem like this you can not have to much information. Let me know if I can be of help.

[4x4 LAND]

Check the playin the shaft of the distributor. Have seen several shaft bushings worn out allowing rotor and reluctor ring to move off center in the distributor causing engine miss under heavy load

[mikeandkim]

Thanks for all your help guys. Problem still continues. No tach just the idiot lights. It only happens when you give it some gas and even then once in a while it does fine. I had a thought to run by you but I can't imagine they are tied in but the timing is right. this started right after the nuetral safety switch was bypassed as I din't want to pay the top dollar for a new one. Any way that could be a part of the problem?