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'91 XJ just shuts off???

J

jw33

NAXJA Forum User
Location
TX
'91 XJ 4x4 with a 4.0 and a 5 spd. pretty much stock with about 133K miles. The truck runs fine, but now it's starting to randomly shut off for no apparent reason. I checked the codes and it doesn't have any stored and I replaced the CPS last week and that has not changed anything. Temperature, speed, RPM, and the fuel level seem to have no effect in when or why it will shut off. It will usually just restart, but it may die in spurts like 4-6 times in a few minutes then it may run for an hour or so with no incidents. It seems like it's losing all electrical power because I notice that the engine RPM's go to about 2K when I restart it like the IAC motor has been reset when the motor is first started. I'm going to take a good look at the ignition coil connections and try to find out if there is a relay that supplies power/ground to the PCM. Any other ideas on where to look???
 
as remedial as it sounds, check your main grounds.
 
There is a relay that sends power to the coil and fuel injectors. Also a relay for the fuel pump. Do you still have the ballast resistor for the fuel pump. If you do, bypass that. It is not needed and will eliminate one more trouble spot.
 
The ballast resistor is still there and I'm going to bypass that anyway even though it's not acting like a fuel starvation problem. It's more like someone just turns off the key for a few seconds and then turns it back on.
 
Well I replaced both battery connections and made sure everything was tight and it still did the same thing. It was sitting there idling and after about 2-3 minutes it just died. I suspected that it is somehow losing the signal from the CPS even though I just replaced it so I took the connector apart and checked the chassis/female side. I closed them up a little bit because they seemed loose and so far its idled for over 10 minutes with no problems. The only thing that bothers me is that I have not had any codes when I check the engine light after it dies....
 
Does the 5-speed have a CPS? Mine 93 automatic was doing this and stopped after swapping the CPS. There's plenty of write-ups on how to do it and it's not very difficult.
 
'96 wouldn't idle the other day, but started fine and ran when i kept on the pedal. Ended up being a fuel filter. I was thinking electrical like you, but it might be worth a 10 dolla shot to see if it fixes it.
 
uvaldetxj said:
check your ignition switch. a switch that's starting to mess up, can **** with your electrical, and turn your jeep off.
Click to expand...


I'm starting to lean towards this area also. I have a feeling my jeep has been almost completly under water at some point in its life after some of the stuff I've ended up finding while working on it..... Next time it acts up I'm going to try wiggling the key around and see if that does anything.
 
I had a problem like this with my Chey Caprice Classic ( I know its not a JEEP) but it was a vaccuum issue. There was a huge hole in one of the vaccuum lines. By the way I now own a '90xj.
 
RedHeep said:
'96 wouldn't idle the other day, but started fine and ran when i kept on the pedal. Ended up being a fuel filter. I was thinking electrical like you, but it might be worth a 10 dolla shot to see if it fixes it.
Click to expand...

This was my first thought... the fuel filter canister needs to be changed periodically.
 
Have you found out anything new? I am having the same problem with my 92 and I've already replaced tps, cps, plugs and wires, fuel filter, and fuel pump and battery all connections and cleaned all the grounds. I am ready to take it to the electrical mechanic. Post if you found the cause.

thanks,
mike
 
Anybody ever bothered replacing the coil? I know they had a huge problem with the Renix jeeps coils being faulty, windings coming lose and shorting out, causing the engine to die suddenly. I don't know if they ever had a similar problem with the post-Renix engines, but anythings possible.
 
Pull the IAC and clean the metal (copper or brass) tip. Careful when reinstalling; those screws aren't hard to break (they're aluminum or something soft and non-magnetic).
Done.
It's the circled area in these pics.
iac.jpg
iac2.jpg
 
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