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Stalling, 1995 Jeep Grand Cherokee Laredo, 4WD 6cyl

Old 09-14-2016, 05:34 PM
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Default Stalling, 1995 Jeep Grand Cherokee Laredo, 4WD 6cyl

I'm having a stalling problem with my '95 Jeep GCL. The vehicle stalls while driving and won't restart for 30-45 minutes. It will then start and run for just a bit before it stalls again. So far the throttle body has been thoroughly cleaned and O2 sensor checked and good. The distributor, coil and crank position sensor have been replaced. The problem remains.

We took it to a shop where they tightened the battery cables and sent it home saying they couldn't get it to stall again. It ran great that night and the next morning. Then it started, drove 10' and died. Started right back up. Made it to the fuel station where it refused to start after being filled up. I may or may not have cried when receiving this information from my son who drives the dang thing. Well, he doesn't drive it now...he drives my truck while his jeep sits. Point is, I want my truck back so I need to figure out what's wrong with his flippin' jeep.

Please help!!!! I'm at my wits end with this jeep. Sure, the transmission needs replaced but I don't see any point in doing that if the vehicle won't run. If I can get this stalling issue fixed, we'll put a tranny in her and keep her for a few more years. Did I mention I'm [I]this[I] close to setting the whole thing on fire? Again...and I'm begging here...PLEASE HELP!!!!
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Old 09-14-2016, 06:31 PM
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Welcome to CF!

This sounds like the typical symptoms of a failing Crankshaft Position Sensor. Maybe a loose or corroded plug on the PCM or cracked solder joints inside the PCM. Just guesses, mind you.

Last edited by dave1123; 09-14-2016 at 06:36 PM.
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Old 09-15-2016, 06:47 AM
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Hi Celle!
Though Jeep is an awesome vehicle, and most seemingly serious problems are actually not, they do require some skill and knowledge. Owning one is not a spectator sport, if you will. You would be wise to find a plugged in mechanic shop to help out. That being said, I agree with Dave, it sounds like your crank position sensor, cam position sensor, or maybe a fuel pump issue, or maybe something else. Always best to troubleshoot to the problem before starting to 'throw parts at it' as that can be very frustrating and expensive. As with any older vehicle that you want to perform like new, there are going to be issues. Hope this helps.
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Old 09-19-2016, 05:45 PM
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Thanks for the responses! After we changed the crank position sensor, the jeep started right up. The boys took it for a test drive two miles down the highway and then called us to come tow them home. There she sat, in the driveway, for a week before going in to the shop. That's where they tightened the battery cables and called me to come pick it up because they could no longer reproduce the problem. My son managed to reproduce the problem the next day at the gas station - it wouldn't start back up after being shut off to receive fuel.

I did get out in the yard take the PCM off while the nine-year-old neighbor girl next door watched and asked if I was trying to fix the car. I saw her watching and hoped she was being inspired, maybe subconsciously understanding that even though men typically work on vehicles, females can work on them as well. Realistically, she was probably just wondering what her crazy old neighbor lady was doing crawling all over an engine and the ground. For the record, that was because I kept dropping my tools.

During my very brief (10 minutes tops) inspection of the PCM, I was able to determine this: I don't know what I'm looking for. I crossed my fingers and reinstalled the PCM as I figured I can do more with a jeep that will only take me two miles before breaking down than I can with a jeep that won't start at all because I shorted out the computer by pretending that I know what I'm doing. Lo and behold, she started after I put the PCM back on and connected the battery. I drove it three miles this time before stalling at a stop sign. So......the doggone heap of a jeep is back at the shop as of yesterday. At least it's in good company - they have another right now with the same problem as mine. I'll post an update if I ever get the problem figured out.
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Old 09-21-2016, 02:08 PM
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Chelle, frustrating isn't it? I am having the same problem as you. I am going to check the PCM in mine this weekend. My troubles started after a new alternator was installed. Not sure if there is a connection between them. Please keep us abreast of the troubleshooting and hopeful solution,
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Old 09-21-2016, 02:37 PM
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I had this problem, along with a myriad of others, some things to check:

TPS - make sure it is giving out correct readings. mine wasn't and every time I let off the gas it would stall.

neutral safety switch if you have an auto - Its super easy to "refresh" it, takes just a few minutes. That cured all of my no starts after short drives. I guess it wasn't getting a good enough connection.
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Old 09-21-2016, 03:56 PM
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Originally Posted by 95quicksilver View Post
Chelle, frustrating isn't it? I am having the same problem as you. I am going to check the PCM in mine this weekend. My troubles started after a new alternator was installed. Not sure if there is a connection between them. Please keep us abreast of the troubleshooting and hopeful solution,
There is a connection, the voltage regulator is in the PCM, I think.
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Old 09-23-2016, 10:46 AM
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Originally Posted by 97grand4.0 View Post
There is a connection, the voltage regulator is in the PCM, I think.
Yes. The voltage at the battery at idle is 13.7 volts, I did not have helper to check it at higher revs, but factory volt gauge does not show any charging issues when driving I think the regulator is working OK. Still could be misbehaving when driving.
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Old 09-24-2016, 09:30 PM
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Today I did some work and investigating on my stalling Jeep. Found a good bit of resistance on ground circuit. I have a replacement battery terminal and found that the wiring coming into it was not making a good connection. Cleaned it and reattached and it made a vast improvement in resistance. Also removed and cleaned ground to body connection at battery. Swapped out the ASD solenoid with another. Checked voltage and ground at TPS coming from computer. Both seemed fine. Drove Jeep for about a half hour test drive and there was no problem!? Is it fixed, I'm hesitant to say yes. Plan on driving more in next few days and see what happens. Moral of story, did you check your grounds?
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Old 10-06-2016, 05:48 PM
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My SO and his buddy checked grounds before changing the distributor and crank position sensor. After we did all we did and still couldn't figure it out, the jeep went to the mechanics shop. The mechanics shop couldn't figure it out either so they took it down the road to "a guy that knows more about jeeps".

He couldn't definitively diagnose the problem but he suspects the computer. He tapped the computer and the jeep died. Tapped it again and the jeep started right up. That was the only time he was able to get it to die so he can't say it isn't just a coincidence. I got a PCM from a salvage yard so I'll change it out this evening and see what happens. I figure it's a 50/50 shot.

95quicksilver, ASD solenoid? Tell me more? How'd your jeep do over the next few days?

Last edited by chelle; 10-11-2016 at 11:10 AM.
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Old 10-06-2016, 07:24 PM
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Did you try to run the self diagnostic on the Jeep? I changed out several items recently on mine and then learned here how to run it and it pointed me straight to the CPS. Changed mine with a OEM Mopar CPS and so far so good. Stalling sucks but it seams to be a common problem.
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Old 10-07-2016, 02:24 AM
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"He tapped the PCM and the jeep died." This tells me if could be cracked solder joints at the terminal strip inside the PCM. Another common problem. This problem started when they quit using solder with lead in it. The lead-free solder tends to get brittle and crack because of vibration and temperature changes. This can be fixed with a small soldering iron or gun and a bit of leaded solder. It's fairly easy to open up the PCM. Check Youtube for videos.
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Old 10-07-2016, 03:09 AM
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Okay, a quick tutorial here. All of the sensors and the PCM electronics work on 5 volts and all of the major outputs go to relays to operate 12 volt systems. The PCM does some switching of 12 volts by grounding those devises. The ASD (auto shut-down) relay controls the ignition and fuel injector circuits and is turned on and off by the PCM. If the PCM looses the signal from the crankshaft position sensor, it shut off the ASD relay resulting in the engine stalling. Any sensor signal loss or malfunction can cause the PCM to decide to shut off the engine. The electronic components in the PCM are better quality than those in your home PC. They are not prone to failure very much other than signal loss or circuit interruptions, such as broken solder joints.

To illustrate what I mean by the PCM switching, the fuel injectors are powered by 12 volts and there are 6 drivers in the PCM that form the grounds for them. The PCM triggers a driver to activate an injector.

I hope this helps and doesn't confuse you more!
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Old 10-07-2016, 10:10 AM
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Originally Posted by dave1123 View Post
Okay, a quick tutorial here. All of the sensors and the PCM electronics work on 5 volts and all of the major outputs go to relays to operate 12 volt systems. The PCM does some switching of 12 volts by grounding those devises. The ASD (auto shut-down) relay controls the ignition and fuel injector circuits and is turned on and off by the PCM. If the PCM looses the signal from the crankshaft position sensor, it shut off the ASD relay resulting in the engine stalling. Any sensor signal loss or malfunction can cause the PCM to decide to shut off the engine. The electronic components in the PCM are better quality than those in your home PC. They are not prone to failure very much other than signal loss or circuit interruptions, such as broken solder joints.

To illustrate what I mean by the PCM switching, the fuel injectors are powered by 12 volts and there are 6 drivers in the PCM that form the grounds for them. The PCM triggers a driver to activate an injector.

I hope this helps and doesn't confuse you more!
So, I looked at a schematic for my Jeep (1995) and it says that the CKS and CPS are actually an 8V circuit. I know in different years and models Mopar used different voltages to control these circuits.

Just adding to the confusion!
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Old 10-07-2016, 10:19 AM
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Originally Posted by chelle View Post
My SO and his buddy checked grounds before changing the distributor and crank position sensor. After we did all we did and still couldn't figure it out, the jeep went to the mechanics shop. The mechanics shop couldn't figure it out either so they took it down the road to "a guy that knows more about jeeps".

He couldn't [/I]definitively[/I] diagnose the problem but he [/I]suspects[/I] the computer. He tapped the computer and the jeep died. Tapped it again and the jeep started right up. That was the only time he was able to get it to die so he can't say it isn't just a coincidence. I got a PCM from a salvage yard so I'll change it out this evening and see what happens. I figure it's a 50/50 shot.

95quicksilver, ASD solenoid? Tell me more? How'd your jeep do over the next few days?
No improvement Chelle. After doing the repairs I described above, I took it out for about a half hour thrashing and no problem. My wife took it out the next day and it died after about a 45 minute drive it died again. Luckily I was able to diagnosis right at time of failure. I was getting fuel to rail, the injectors were firing, but I had no spark. Pulled coil. looks like it was OEM. Had plenty of hairline cracks around core (part that bolts go through to mount). Checked ohms with a heat gun blowing over coil. At ambient temperature the primary and secondary were both in spec. added heat, and they both climbed with the primary jumping all around. Think coil is faulty and have a new MSD on the way. Will install this weekend and let you know.

See Dave1123 description about ASD....
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