Intermittent Stalling/Dying While Otherwise Driving Fine...Restarts, Drives, Randomly Dies Again.

[BlueDove91]

(Truck: '91 MJ 2wd 4.0 HO, SB Base)

SOLVED:

I want to make this post to add into the pool of what is already available for those who are experiencing a similar issue and trying to troubleshoot it. 

 

Several weeks ago, I was driving home going around 40 or 50, when suddenly my truck just shut off. The engine just stopped. I lost all acceleration, but the power was still on. So I pulled over to a stop, turned the truck off, waited a few seconds, and cranked. It started right up. Scratching my head, I shifted into first and pulled back onto the road. I hadn't gone 20 feet before it died again. This time I tried to restart it, and it would crank but not turn over. I shut it off, waited a minute or two this time, and then tried again. It started up just fine, and I pulled back on the road and drove home with no further problems.

It seemed so bizarre to me. I felt that dread surfacing in my gut of "oh no, what is going on now...". I'm sure you know it. But I wrote it off as just a glitch of something. 

After that, the Comanche drove fine for a while. I did feel an occasional "hiccup" here and there, where it seemed to lose power for just the slightest moment, but would correct itself and was fine afterwards.

A couple weeks later, I drove to do a job, finished, went to the store...and when I came back to load up the groceries and go home, the truck started up and then died right away in the parking space. Again, I restarted it, and managed to get out of the parking lot and into traffic -- and it dies again right as I'm entering a roundabout. 

Now it cranks but won't start, so I wait again... and it eventually starts up. I'm several miles down the freeway, going about 65...and it dies again. Power steering goes out, the truck won't restart, I almost run off the road because when turning the key to try to crank it the steering wheel locks up and I suddenly forget what to do. 

Anyway...scary stuff. I managed to pull off safely. Again -- waited a few minutes, until eventually it cranked and turned over, and I was back on my way. 

 

I eventually made it home. But the grace period with this intermittent issue had ended, so it was time to research and fix it. 

As is frequently the case, there were many different opinions/suggestions about what could be the ultimate source of this issue, as well as write-ups from people over the years troubleshooting and chasing all kinds of different things, often to no avail. 

 

My issue wasn't a goose chase, thankfully. But I wanted to post about it in hopes to give one more scenario/solution for this problem. I didn't see anybody post *specifically* about what turned out to be my issue. 

 

With that said: 

The issue DID end up being the Crankshaft Position Sensor. 

BUT, what threw me off was that I had replaced the sensor just last year...as well as the TPS, IAC, Plugs, Wires, Cap, Ignition Coil, Fuel Pump, Fuel Filter, 02 Sensor, Fuel Check, Fuel Pressure Regulator. I did it all. 

One thing that helped me was the thread that showed the list of OBD codes, and how to initiate the code sequence. 

It DID give me a code that had to do with the CPS ( I think code 11?), so at least I figured I'd start there before trying other things. 

I tried using a multimeter to check the CPS...but for the life of me I have still not figured out how to use a multimeter. I'm not even sure mine works right. It didn't tell me jack squat. So I just decided to take the CPS off and replace it. 

 

Once I took off the old CPS, I quickly discovered what the problem was -- in the area where the wires feed into the sensor, the plastic sheathing was worn through and the metal wiring was exposed on all three wires. That would do it, I guess. 

It doesn't seem like there is anything near the wires that could cause friction enough to wear through that sheathing. So I'm assuming it was a heat thing and it just melted through? The way they made the part, they put that corrugated plastic sleeve around the wires, but it doesn't cover them all the way -- it is too short, and leaves the wires exposed at either end (sensor side, and/or plug side). 

 

Anyway, I wrapped silicone self-sealing tape around the exposed area of the wires on the new part in hopes that it will protect it better this time. Because that part wasn't even a year old before failure. 

After putting the new CPS in, there have been no further problems and the truck drives great. 

 

I'll attach some pics of the old CPS here as well to show the issue.

Thanks for reading, hopefully this helps someone. 

 

** I guess one final thought would be: anyone know how those wires could become exposed like that in just a year's time? And so close to where they enter into the sensor? Is my theory about heat/melting the most plausible? Or should I be concerned about something else that needs to be addressed which led to this happening?

Thanks.

 

[pizzaman09]

I am glad you got this sorted out!

 

Random theory since I design rubber parts for a living:  So the cracks are on the outside of the bend on the wires.  I'm guessing the wires were bent over hard in their installed state.  The wires are coated in some sort of rubber, rubber in tension like in the outside of a hard bend is highly susceptible to ozone attack which will make the rubber crack.

 

I doubt it's abrasion because the sensor body looks untouched.

[M.T.Hands]

^^^^ I agree, have seen other installations in different applications that have done similar, some only being exposed to enviromental elements (no engine heat)

 

somebody the other day on the (is a Comanche reliable enough to DD thread) mentioned buying a later model vehicle as their DD, what is sad is none of the stuff being produced today will be around and the electronics are going to make them junk, you can find an old 80 year old tractor that is and will still be running, can you imagine doing any of that with the newer junk, Plastic and rubber just naturally degrade over time, although IMO you sensor should have held up longer, But I read of and have experienced more electrical failures with later model junk, not to mention rodents liking to feast on wiring on equipment

[gogmorgo]

Obviously all we can do is speculate, but I’d agree the wires likely were bent and pulled tight when installed. It’s also a stress concentration point and vibrations flexing it back and forth will do damage. It’s pretty common to see this sort of damage on sensors and connectors, anywhere wires are held firmly in place at the end but allowed to wiggle around.

Its also possible it happened when they were bundled and jammed into the box. Some of these parts sit on shelves for years, and just unbending the insulation can sometimes cause damage.
Just a little nick in the wire plus some road salt and corrosion will end the life of the wires in a hurry. The coiled wire in the sensor is tiny and won’t take much to corrode through.

I’ve also seen similar damage from wire-piercing probes. The only context you’d do that is testing so unless someone installed and tested it and put it back in the box that’s unlikely. 

[Ωhm]

Were wires ever poked with a testlight or DVOM needle probe?