[lyleorszulak807]

89 jeep cherokee 4.0L auto. replaced fuel pump + fuel pump relay and CPS. currently the jeep will start and drive then all of a sudden the jeep will die while moving. Sometimes the jeep will start right back up other times it takes a few minutes and a few starts. Havent had the chance do diagnose when happening because Ive had to move the jeep from the middle of the road. When I try to restart the idle is extremely rough and the RPM's will not increase no matter how much pedal I give it. I then shutoff and restart the jeep, after a few times the jeep comes to life and all is fine until next time. Has not occured on the freeway yet (although sometimes I do feel hesitation, both motor mounts are no more hence I feel alot) ...only on the streets. Ive looked all over the forums and I hear so many things..IAC, TPS, some sensor in the distributor....etc. Please help if you have any idea on what this might be, jeep is a daily driver.

Thanks,
Lyle

[lyleorszulak807]

Searched around and printed out a few instructions on how to test various sensors which could be causing this, any suggestions would be much appreciated.

Thanks,
Lyle

[Brassmonkey]

Try the throttle position sensor.



Sounds like a problem I had.

[kiwicowboy]

Check the crank sensor that is located on the top right of the bell housing. If the sensor is still tight but the boot is gone, could be crud on the flywheel.

[kiwicowboy]

My bad, the sensor is on the top left.

[tangofox007]

I had a similar problem. Mine would tend to stall at idle, like when stopping at a traffic light. A new TPS fixed it. One thing for sure: if your TPS is original, it has done its duty.

[lyleorszulak807]

Thanks for the replies. I already replaced the crankshaft position sensor. Although I didnt put the boot back on..... Ive looked on the internet and I hear two different sides of the story. Is the fuel pump relay the second from the front of the vehicle? I swapped the relays again yesterday as I had to drive out to palmdale and it hasnt stalled yet. We will see today....

[tangofox007]

I can tell you from experience that the order of the "four relays" sometimes varies from the order shown in various publications. Mine did. And I am the original owner, so I know they came from the factory that way.

[tjwalker]

I agree with some of the other posts. TPS definitely comes to mind first as a sensor issue.

Also, I know that the crank sensor has been replaced but you may want to ensure that the electrical wiring/connector for the CPS are in good shape as well. I've seen a situation where the sensor itself was good, but the entire circuit is only as good as the weakest link.

Although you mentioned the symptom of running rough when started doesn't really match up with the crank sensor, my guess is that it is something else. Start with testing and or replacing the TPS>

[myriad360]

Originally Posted by Brassmonkey

Try the throttle position sensor.



Sounds like a problem I had.

Yep. Second that. Before you go replacing it, test it, it might just need adjustment. Something you'll have to do with a new one anyway.

[lyleorszulak807]

Have been working weekends and no time to play with jeep. Did the same thing the other day and had to leave it parked on the street since it wouldn't start.

Going tonight after work in attempt to get some voltage readings, bought a new TPS just in case. Will give a update tomorrow.

Buddy just bought a 90 XJ with stroker for a 1000!! unbelievable deal. although it sound like the transfer case chain needs to be replaced.


Lyle

[lyleorszulak807]

Went to go play with the jeep last night, now it wont start completely. Tried replacing the TPS, but the bottom screw is stripped. So I removed the cap and rotor and noticed they were aluminum contacts and some sings of wear and tear.

Bypassed the resistor on the fender wheel, no change.

If the TPS went bad would the jeep still start?? I would imagine so.

Also took out the ECU, going to swap with another buddys XJ.

Lyle

[myriad360]

TPS could cause a no-start, but it should still crank.

Start doing spark tests versus fuel test. Make sure there is spark and fuel in the chamber. If one is missing, start at the bottom, and work your way up. (Ignition: Spark from the coil; Fuel: pressure from the pump). If both are there, but it starts hard or no start while cranking, could be a bad mixture. Clean your plugs and try again. If it is rough or seems to be running rich, its emission sensor time. That is everything from a TPS to a CPS to EGR. Get an FSM and check ECU input for this. You are a Renix, so I can provide this for you if you get this far.

[lyleorszulak807]

There is spark and fuel, already checked. Just cranks and seems like it wants to start but doesnt, as if the timing is incorrect. But remember it has never not started before, so something broke completely.

Taking my multi meter with me today and going to check the voltages on the TPS, work sucks when ur here every weekend.

Lyle

[lyleorszulak807]

Checked the TPS sensor, was at .8v with throttle plate closed and went up smoothly to 5v at full open.

Replaced cap and rotor and still wont start but cranks. This led me to ignition coil.

Although I have spark is it still possible im not getting enough spark? I measured the resistance and found the primary resistance to be .7ohm and secondary resistance 7kohm. I looked up the specs and it should read .9-1.2 ohm and 11k-13.3kohm. Could this be my issue? Im kinda stumped at this point, going to replace coil tomorrow.

Lyle