2000 xj wants to die at stoplights

2000 xj 4.0 auto 86k miles on it. Sounds like it has a missfire, Idles rough, seems like it is going to die if left in gear at a stoplight. No check engine light. It seems to drive fine the only problem is when it is running less than 2000 rom. Anyone got any ideas?

less than 2000 rpm

sounds like a possible bad TPS to me

I would thoroughly clean the idle air control, idle air control seat, and throttle body. Then test your throttle position sensor; just need a simple meter for that. Also, review basic tuneup stuff when symptomatic.....when was the last change of spark plugs, distributor cap, rotor> Test fuel pressure at schrader valve on fuel rail if you get stuck....This is a process of elimination. Good Luck and post back what you find!

today after work i cleaned the throttle body, runs a little better now but still seems like it wants to die when im stoped. I tried to test the tps but i cant get my multimeter to give me a reading with the connector hooked up like it says to in the manual (back probing). I got a reading without it hooked to the wiring It was 4.10 opened all the way and i forget exactly what it was closed but it wasnt what the manual said it should be. I am just wondering If i should replace it or not since the manual says to have it hooked up with the ignition on when you test it. the plugs were just changed not too long ago. It doesnt have a distributor it has the coil packs. Any thing else i should look at? I dont have a fuel pressure gauge so I guess ill pick one up when i get a chance.

tim1985 said:

I am just wondering If i should replace it or not since the manual says to have it hooked up with the ignition on when you test it.

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if its like my 89, ignition on means to have the key to the "on" position without the engine running. it sounds like you tested it correctly and the tps is out of spec. i hate back probing the harness so i carefully cut staggered sections of the insullation so i have about 1/8" of the wire exposed. when done testing i use liquid electrical tape to cover up the exposed wire.

**update** the check engine light came on today so i picked up a scantool, It says code p0302 cylinder #2 misfire any ideas what the problen could be?

miss fire at a cylinder could be a bad spark plug, injector, coil pack.

do a search for heat soak to give you an idea about the misfire problem. miost times the heat soak is on the #3 cylinder.

have you checked the plugs?

For the record, you can backprobe the TPS with a paperclip. Much better than cutting the insulation on the wire.

Or, you can test it at the TCM.

Focus on the check engine light. The fact that it came on at the same time that your engine is symptomatic is probably not a coincidence. I'd change that plug or at least inspect it and swap it to a different cylinder as it's easy to do. Also, consider swapping coil packs between cylinder 2 and say cylinder 5 to see if the misfire follows to that cylinder. "Swap and follow" is a tried and true troubleshooting strategy.....
Keep us posted.