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  #1  
Old July 19th, 2018, 16:51
Wyvern Wyvern is offline
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One-time stall

Hi guys,



I was recently leaving work after starting my '96 XJ flawlessly. I got about 600 feet when my jeep died completely with no warning.



I tried to start it up again and it came to life and immediately died out. I tried once again to start it--same deal.



Then, I started it up and as it came to life I added a little gas while in drive still and the check engine light came on, but the vehicle stayed on and drove like normal.



The engine light went out after I got home and started the vehicle again and I have not had any problems since and no more CELs.



My scan tool showed that I got a thermostat code (stuck open), which I knew about, as well as a camshaft position sensor code (which is just a pick-up coil in our XJs).



What's strange about this is that I just replaced the entire distributor/cap back in October of '17.



I'm a bit nervous about this because a vehicle dying mid drive can be potentially very dangerous and I'm driving back to my hometown 9 hours next week.



The only other issue my XJ has is, being a '96, it has a pressure regulator valve in the fuel pump assembly instead of on the fuel rail. It has been bad for a while, forcing me to do the "poor man's prime" method of turning the key forward a few times before turning over the engine.



My first thought after stalling was that the Jeep had leaned out and wasn't getting fuel, which would explain why giving it some gas put things back in order. However, upon returning home I checked the line pressure at the schrader valve with my pressure gauge and got 49PSI bang on while the Jeep was running, which is perfectly within spec.



Any thoughts guys? I want to hear some more opinions before I simply replace the pick-up coil under the distributer cap. I was going to be safe and simply replace the crankshaft sensor as well, since they go so often and can produce the symptoms... however the fact that the jeep started up after stalling leads me to believe this isn't a CPS issue.



Thanks guys, I'm so glad to be part of this awesome community after many years of spectating the forums.



-Wyvern
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  #2  
Old July 19th, 2018, 18:12
trippled trippled is offline
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Re: One-time stall

I could totally believe it to be a bad crank sensor. They can do some bizarre stuff. depending on what the computer saw they can be a little undecided on what code they throw. Seen many cam codes for bad crank sensors. That's where I'd start.
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Old July 19th, 2018, 18:34
Wyvern Wyvern is offline
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Re: One-time stall

Quote:
Originally Posted by trippled View Post
I could totally believe it to be a bad crank sensor. They can do some bizarre stuff. depending on what the computer saw they can be a little undecided on what code they throw. Seen many cam codes for bad crank sensors. That's where I'd start.

Thanks man, I'll start there. I've had zero issues driving it the past week.
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Old July 20th, 2018, 00:34
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8Mud 8Mud is offline
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Re: One-time stall

Just a couple of thoughts, the cam position sensor and the CPS share the same input voltage, along with the MAP and the TPS. If one or the other partially shorts, it affects the others. Low input voltage can cause issues. But often the CEL quits all together when there is a short in the CPS/cam sensor input voltage circuit. Best guess is some of the drivers in the computer overheat and have some sort of protection built in which shuts the drivers down, one of the side effects is the CEL quits also (no power at all, no check bulb function when turning the key to the run position) . The input voltage for the CPS and cam position sensor may fail incrementally and IMO there may be a fine line between a little and too much failure.

If it stalled relatively cold, it may be the IAC. Mine would periodically stall cold, but after it warmed (the gunk in the IAC) a little, no problems. My trick was to start with about 1/8-1/4 pedal, so the IAC wasn't starving the engine of air.

On many models the O2 sensor CEL can be intermittent and not set a code. Or in other words the CEL may only come on when the O2 sensor is out of operating range. My 96 transitions from closed loop to open loop after driving about a long block. It would sometimes act up or die during the transition when my O2 sensor was failing.

I don't trust CEL trouble codes much, because many of the sensors share an input voltage (violet/white, 5 volts) and the failure (low resistance, partial short) my be caused by another sensor on the same input voltage tree. One sensor may be a little more tolerant of voltage input and may not trigger a code, another may be more sensitive but still be good.

One thing I noticed when I replaced my distributor was that the cam position sensor was used, not new. Everything else in the distributor looked new. I kept my old cam position sensor when I turned in my old distributor for the core charge.

For some codes the CEL stays on, for some it comes on and then goes out. My code lists don't agree, which leads me to believe this may change some year (model run) to year.

Right after startup mine would stall. Sticky IAC, no code.

After a block of driving mine would either run really bad or stall. O2 sensor no CEL or intermittent CEL, no code set.

Random and sporadic fail to start or running really badly or quitting altogether. Was a partially shorted CPS, with everything connected I had 2 volts +/- of input voltage. Sometimes I would get no check bulb CEL when turning the key to the run position, sometimes I would get a code.

Once I had an oil leak at the back of my valve cover gasket, my CPS was covered in gunk, oil and grit. I sprayed the CPS off with brake cleaner and replaced the valve cover gasket. My CPS issues disappeared for years, same CPS.

It may be your cam position sensor, it may be something else. Swapping out sensors is usually my last resort, not my go to.

Maybe I've helped a little? Maybe I just confused you?
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Old July 20th, 2018, 04:02
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Tim_MN Tim_MN is offline
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Re: One-time stall

You cannot properly trouble shoot with existing faults/failures. Fix any known issues. Only buy genuine Jeep OBD sensors.

A faulty Coolant Temperature Sensor can cause starting and driving issues. Test the sensor and inspect the wire plug/harness.

Test the O2 sensors and inspect the wire plug/harness.

Random stalling is most often a faulty Crankshaft Position Sensor. Once off idle, IMO the IAC shouldn't cause any stalling. I have had a couple of faulty IAC, the symptoms were either slow to drop idle speed, or hick-ups in the idle when stopped.

Inspect and test the CPS, IAC and the Cam sensor. Visually inspect the wire harnesses for melted or cut insulation, and inspect for loose wire plugs, damaged/pushed back wire pins, and corrosion.
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