What causes a TPS to go bad?

:worship: First of all About 2 months ago I had some issues and ran a ODB1 scanner on the ECU and it turned up 2 codes. One was for the TPS, and one was for the MAP sensor and they both were supposedly running below minimum recommended voltage. I replaced both of them, disconnected the battery for 20 minutes and then reconnected the battery. It ran better for about a day or so and the check engine light started coming on after warm starting. I ignored this (thinking that I had incorrectly cleared the ECU) and after many headaches as of late I decided to figure out what the codes were. It was the TPS (again) running below minimum recomended voltage. The O2 sensor is fine. The problem im having, is that when I first drive the jeep up to operating temp and (for example) stop by the store, go inside for 15 minutes or so. I will come out 15 minutes later, I can start the jeep the check engine light comes on and it seems to idle fine but as soon as I try to drive away or put it into reverse it just stalls and dies. I usually have to wait 30 -60 minutes before starting and driving away again. Also, I started driving places and not shutting it off, but now it doesnt stay idleing for more than 7-8 minutes before choking and dying. If im really in a hurry I can seem to pop the clutch and it will run fine( the check engine light doesnt even come on???) Dont get it? Im not sure if my TPS is to blame, but id still like to find out why my TPS went bad after a day or so. By the way, I have a 1994 XJ 5-speed with the 4.0L with 216,000 miles completely stock. Thanks for any input.

nvm

Moisture I would say is the #1 cause of TPS failure.

The reverse thing makes me think CPS.

xylonjay said:

Would a CPS throw a code?

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Sometimes. If you're lucky, then yes. Most of the time they don't. They usually die while driving down the road, or one morning you'll go to leave somewhere and have a dead jeep.

:doh: sweet

How hard are they to replace on a manual 5-speed. factory (no lift)??

xylonjay said:

:doh: sweet

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However, I went back and re-read your post. I've read several cases where people's Jeep's would die driving down the road, and after they let it cool back off a bit, they'd fire right up like nothing was wrong, get down the road a little ways and once it warmed up again, it shut back off, and the problem turned out to be the CPS.

Something to definitely search around here for and look into with your situation.

#1 cause of sensor falure is moisture (electricty and water dont mix) also not only do you have to clear the codes you ecu need to relearn its parameters when you change the tps or cps if the tps is new then put a $15 or so cps on it. it's easy 2 bolts 1 plug proly 10 mins. good luck hope you get it figured

Ive been looking all evening (4hrs) Ive seen alot of things pointing to coolant temp sensor, or mabey even the fuel pump. I havent tested the pressure at the rail. I'll check in later to see if anyone else adds anything. I reall appreciate the help.

xylonjay said:

How hard are they to replace on a manual 5-speed. factory (no lift)??

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i did it from below with long extensions and alot of patience

99XJSPORT06 said:

However, I went back and re-read your post. I've read several cases where people's Jeep's would die driving down the road, and after they let it cool back off a bit, they'd fire right up like nothing was wrong, get down the road a little ways and once it warmed up again, it shut back off, and the problem turned out to be the CPS.

Something to definitely search around here for and look into with your situation.

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I agree my girlfriends jeep did the same thing right after we hav the trans. re-biult she calld me all freaked out when her jeep died on the freeway the cps was cracked when the shop put in her trans.

xylonjay said:

How hard are they to replace on a manual 5-speed. factory (no lift)??

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not bad a wobble socket and a long extension makes it a piece of pie....... and skinny arms help when I did mine I un-bolted it from under and pulled it through the top to easly un-plug it. Ramp or jack it up for sure.

xylonjay said:

Really? It has to relearn parameters? Dang so is my TPS neccasarily shot if its throwing a voltage code? Mabey bad ground? Im pretty stumped as usual

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could be loose or just bad i think its grounded through the ecm not really sure about that though.

Cool. Thanks for the tips. I'll keep i'll post more after checking a few other things Thanks again.

I would bet money it's your crank sens. with an auto trans. to relearn all yur do it fire it up put it in drive and pull the brake let it sit for five mins and you done. 5 speed I not sure how yet to relearn.

:guitar: Thanks for the link. Well after reading ALOT about my possible options, Ive narrowed it down to a bad Coolant Temp Sensor. Last night on my way to go ice fishing, my girlfriend need to stop by the store and I had to wait outside with the truck running. Well, eight minutes passed and the XJ choked and died. I could start as usual with no issues, but trying to drive away was a different story. I then had an idea. After reading about the coolant temp sensor, I decided to try and cool of the sensor by applying a dirty, crusty, piece of snow I broke off of a snowbank, and applied it right to the sensor. After 5 minutes I was back on my way. XJ fired right up and no check engine light came on. I am going to replace it this weekend and hope it works ***fingers crossed*** Thanks again everyone and i'll report my success or failure.

I am going to go out on a limb here and say the CPS and CTS are OK. Your initial and final OBD-I data says low TPS voltage and the original said TPS and MAP low voltage. The TPS and MAP sensor have a common return wire to the ECU, so if both sensors are new that levels a poor connection somewhere between the MAP, TPS and the ECU on that common return signal wire, or on the ECU hot wire feeding those two sensors.

You can do simple tests with a high impedence digital multimeter, about $5 at Harbur freight, and get the probes reading the input and later the output voltage from those two sensors while wiggling wires and connectors in the wiring harness. The fact that the problem stopped temporarilly after disconnecting and reconnecting the battery is also an indication that you may have connection problems even at the battery.