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CPS failure?

1990JEEPXJ

1990JEEPXJ

NAXJA Forum User
NAXJA Member
Location
San Diego
so my XJ has had an intermittent issue with surging/missing in OD from about 45-65 with about half throttle. it also doesnt always idle smoothly and hesitates and runs a little rough off idle when this happens. the idle isnt low, its actually high, i know the IAC needs replacing but i dont think its a contributor here. the plugs arent that old and the one i checked looked good. the cap and rotor arent old either. the symptoms point to the crank position sensor but i wanted to get other ideas. i recently actually replaced it with an autozone part and it seemed fine for about 2 days but i figure maybe its possible that wasnt the problem and that its something else i need to address.
 
Sounds more like a throttle position sensor. Usually have a cps get hot kill the jeep it's cools and the jeep starts. Never had it do what your describing.
 
How about spark plug/coil wires? Replaced fuel filter lately? Gotta make sure tuneup stuff is up to snuff so that you're not chasing your tail.

#1. Test your fuel pressure. Compare to factory spec.
#2. Test your throttle position sensor with an analog meter and look for flat spots as the throttle is applied.

My gut feeling is that your problem is not crank sensor related.
 
Is that the 1990 that your name suggest? Renix, I suppose. Renew all grounds by taking off and cleaning. It fixes a lot of issues on those. If it still isn't right, start unplugging sensors one at a time. If it runs better when you unplug one, that's your culprit.
 
After checking those grounds if you still have the problem then check that the manifold is properly torqued down and thirdly if the problem persists then the TPS is your next step. The first two cost you nothing but a few minutes. They should be part of your regular maintenance schedule anyway.
 
Are you sure it is surging/missing or is the tq lockup kicking in-out?
 
yes its a renix. thanks for the suggestions. and the TPS is a new mopar replacement. i will check the adjustment. i will also check the ground and the fuel pressure. the fuel filter is also fairly new. one question, where does the gound strap mount to the head?
 
on the rear-most, drivers side head bolt. It should have a threaded stud on the top -the "Renix killer" is nutted in place on that stud and runs directly back to the firewall. It's a braided steel strap.
 
Shorty said:
on the rear-most, drivers side head bolt. It should have a threaded stud on the top -the "Renix killer" is nutted in place on that stud and runs directly back to the firewall. It's a braided steel strap.
Click to expand...

I like to call it a "braided steel crap", replace it with a heavy guage cable.
 
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