jeephammar

I have a 1987 Jeep Cherokee Chief with the 4.0 in-line 6 cyl., fuel injected, 5-speed. I've owned it since new, and it's completely stock, and has been mostly trouble free for all of it's 230,000 miles.
Recently the engine started cutting out. It will do it at any RPM, and if sitting in neutral or driving down the road. When it cuts out, the tach instantly drops to zero, and the shift indicator light flashes on for a second. In fact the shift up light will flash on even when idling in neutral, the tach drops, and the engine dies. It starts back up immediately, either with the key, or if rolling down the road, it will gear start itself.
I took it to the Jeep dealer, and they couldn't diagnose the problem. They told me that this model of Jeep was too old to store fault codes, and their computer was of no use. But the technician suggested I change the crank position sensor, so I did, but no luck. I also put a new fuel pump in the tank as the original was getting noisy and someone suggested that it might be the problem.
It's cutting out more and more frequently, and I'm sure it's about to leave me stranded. Anyone got any ideas?

Klroach92

when it cuts out is their any jerking stuttering etc...? or does it just die like you flipped the key? has it ever done this in neutral at idle? have you noticed the weather when it happens? only rainy days or does it not matter?

67 GMC

If it just dies when running (like it was switched off), it sounds like an electrical issue to me. These Jeeps are notorious for bad grounds. Cruiser54 has plenty of links on this site to run down electrical issues. I would start by opening the hood while it's running and just jiggle connectors around the ignition module and the C101 connector (the big wiring harness that plugs in under the hood on the drivers side firewall). If it suddenly dies when you're doing that, you'll narrow down the cause.

The Renix doesn't store codes so they can't diagnose it unless it died when the DRBII was hooked up and they got a fault code then. I've got an Snap On MT2500 that works with the Jeep but a simple digital multimeter is fine for most of the troubleshooting.

cruiser54

Here ya go. Click on the "pink link" in my signature. Do the free and easy procedures in Posts 1,2,3,4, and 5 before anything else. Don't skip any steps and take no shortcuts. Replace no more parts until this is done. .

jeephammar

Thanks all for your prompt replies!
Yes - the Jeep will do this (cut out) at idle, in neutral, during any weather conditions. It also does it at 60 mph (or any speed), you never know when. It does seem to become more frequent as it warms up. It only happens occasionally when cold, and then more frequently after being driven across town.
It actually cuts out faster than if you shut off the key. The tach drops to zero faster than the engine can die. And I get that weird shift light simultaneously. I've wiggled all the wiring while it's running and it doesn't make any difference - it doesn't cause it to cut out.
Thanks very much for the tips, and the link. My next step will be to check and clean every ground and connection I can find. After that, the dealership said I might try replacing the TPS and the MAP sensors. Then the ECU after that.
- I hate throwing parts at a problem. I wish it could be properly diagnosed, but it actually cut out and died while the dealership had it hooked to their computer, and they still couldn't figure it out.

cruiser54

Don't throw parts at it at all. For sure it's not a TPS. Could be a CPS, but that can be checked. spend some time on the write-ups. It's a pro-active approach and you could be rewarded with a fix!!

Klroach92

do you have a voltmeter or multimeter whatever you want to call it. I would check resistance on your connections it 100% sounds like wiring or a bad cps possible camshaft sensor also. i would say no to the tps thats more associated with erratic rpm jumping stalling etc but not as you describe cutting off.

cruiser54

Renix has no cam sensor.

jeephammar

Thanks for clarifying that about no cam sensor. I thought for a minute I was missing something. And I did replace the Crank position sensor - I assume that is the CPS referred to here. Still cleaning grounds and connectors. I'm actually installing extra ground straps as suggested too.
I'll let you all know if I have any luck.

Klroach92

Thanks for the info i have not worked on any renix engines just trying to help out

cruiser54

Keep on trucking with the grounds and connectors. we will figure this out.

cruiser54

I know. Just didn't want the OP to go buy a sync generator for his REnix unnecessarily.

jeephammar

Hey all - just wanted to thank everyone for their input. I tried everything listed in Cruiser 54's "Pink Link". I worked on the damn thing for a solid week, and it was still intermittently cutting out, so I finally threw in the towel. I took it to a place called Automotive Electric, and made an appt. Then the next day, I drove it to a destination an hour and a half away, and it ran flawlessly. It seemed that my problems were solved simply by making the appt. Then on the way home, it cut out about every 5 miles, all the way. But it ran flawlessly the next day - when I took it in to the shop. Anyway, the shop got it to fail about 5 times, and ran some tests, then plugged in a re-man computer and left it bungee-corded in front of the shifter (because it's a pain in the rear to get in and out), and told me to go drive it for a week. I put 200 miles on it without a single failure. So I took it back, they re-installed the original computer, and it cut out again - so it wasn't the connections into the computer. So they re-installed the re-man computer, and I drove away a happy (but poorer by $350 - parts and labor) man. It's still running flawlessly today. Thanks again.

cruiser54

Thanks for the update. Well done.

67 GMC

Glad it worked out for you. That's always a tough decision point. You assume one part is good and everything else is suspect or you have to rule out every single part by substitution. $350 is not too bad considering all the time you would be still putting into it to get it to work.