I have a Jeep Cherrokee 1998 4.0 that keeps throwing a Intermittent CKP CPS error. The truck runs fine when cold even slitely warm then all of a sudden
it will start but not run once put in gear. I have replaced both sensors. Truck runs fine fine for a short time then stops running and throws an error.
Any ideas on what would cause such an error code if it is not the Position sersor?

 

I would try changing the crank sensor again and check the plug to make sure it is plugged in good . what brand sensor did you use ?

 

Post the exact code number here.

There are a couple of codes related to the crank and cam sensors; the devil is in the details with OBD codes.

 

1391 error code
First replaced it with a cheap Crank position sensor. it then ran worse so I bought a Master Pro sensor at autozone.
Ran much better. Then started acting up again. Seems to get worse if the engine is hot. I checked for air leaks
and found one fixed it and ran better but still stumbles a lot once warmed up. At full throttle it still acelerate good
once the RPM's come up. Seems like a fuel mixture issue ....but not getting any error codes for that. I do get some back fires
so maybe another sensor is in order????

I have replace the cam sensore also it was the first thing I replaced and it mad no change.

Ron

 

So a little more info. My thought now is the CPS if fine. I think the engine is heating up and starting to run
very rough ( Back fires stumbles surges) when it does this I think it is tripping the CPS giving an error code of intermitante
signal 1391 . So now I am looking in to a full tune up on the jeep to see if this is the problem and not the sensor.

Any one else have any thoughts On why the truck runs great cold and very bad warm?

 

So a little more info. My thought now is the CPS if fine. I think the engine is heating up and starting to run
very rough ( Back fires stumbles surges) when it does this I think it is tripping the CPS giving an error code of intermitante
signal 1391 . So now I am looking in to a full tune up on the jeep to see if this is the problem and not the sensor.

Any one else have any thoughts On why the truck runs great cold and very bad warm?

 

Harness/wiring/connectors

 

Why would you think Wiring? I just do not see the connection here. No that is not a pun. Seems to be
something when the engine heats up. Not knocking your help just like to see the connection .

 

Have you check fuel pressure ? and the O2 sensor ? It could be going lean when it warms up . also did you check all power and ground wires , bad connections can do some strange things .

 

I hear people have issues with non-mopar sensors. Maybe try a mopar brand sensor

 

Mopar is best. Like said, check the wiring, etc..

Damaged wiring, a loose connection or corrosion will cause trouble. The voltage has trouble getting to where it needs to be. Drivability starts to suffer as the PCM is very sensitive to this sort of thing, and can make incorrect calculations based on the signals its receiving, or not receiving. A sensor can work perfectly, but if theres an issue with the wiring, etc., bad things start happening. This is why its always a good idea to check the wiring before replacing sensors. Even fuses. Out of curiousity, check the O2 sensor heater fuse in the PDC. I have heard of that causing trouble once the engine warms up.

 

http://www.learnabout-electronics.or...istors_01a.php

"However, materials that are classed as CONDUCTORS tend to INCREASE their resistance with an increase in temperature."

 

So I disconnected the O2 sensors and the truck ran fine even after Warming up for over 30 minutes of driving . Then it got a bunch of error codes 443 error Evapcanister
Miss fires in all cylinders Crankposition sensor intermittent. O2 sensor errors Yea they are disconnected I thought I had it now It Bearly runs again.

Thoughts bad ground
ecu going bad.
O2 sensors bad

Things tested so far Reattached one ground cable
Clean battery terminals.
2 Crank position sensors
1 cam position sensor
new spark plugs
Did compression test all cylinders 135-150 .
Fuel pressure 50 psi and holds fine.

 

So I found the problem. A ground Wire had rubbed up against the fuel rail and was working intermittently.
I re did all the ground wires and hunted for hours but finally found the culprit . The ground wire was broken but was
just making contact. Never in my wildest dreams would I have thought that wiring was the issue since I thought it was a
heat Issue . From the start. Best guess is the wiring would heat up and break the contact.

On side benefit with the ground cables cleaned it turns over much faster.

 

Thanks for posting the fix .