buddyjaet

After reading many, many, many posts, some really interesting and some were even useful. But nothing offered so far has helped me fix the problem with my Jeep. So here comes the details best I can recall so far.
Purchsed a used but well cared for 4x2 with 174000 miles, no evidence of going in the mud and the previous owner was not one to take it such places, they used a local mechanic for all service work.
I was in the process of doing all the maintenance work normally required for any vehicle, especially a 16 year old used one. Plugs, wires, cap and rotor were replace just prior to my purchase and still had that new smell on them. Previous owner had new tires put on just for me!
After a week started to have issues, it would stall. OBD2 scan tool says P0351, visual inspection of the coils shows massive cracks, so it seemed a reasonable part to swap. Based on the code and the cracks, Autozone part installed. Problem went away for a few days. Next item the fuel filter required replacement, it was in the repair queue already but forced me to swap the part on the side of the road, it was filthy and appeared to be raththe 13ther old, no other issues from that swap. Now owned it about two weeks so far, started to stall after about 8-10 minutes of driving. Would lose power and some of the time catch and keep going, some times had to pull over stop shut down and then it would crank up and run fine the rest of the day. Road speed did not appear to be a factor, happened at 30MPH and 65MPH all in that 8-10 minute window. I was in the process of cleaning the engine compartment in a slow and deliberate manner to see if I had a suspect connection or frayed ground wire or ground point. Nothing obvious presented itself. End of the third week of ownership, on Friday the 13th of course, had to jump start the vehicle as battey was weak and wouldn't turn it over, jump box got me started fine. Left it parked all day, that afternoon it wouldn't turn over at all, battery read 9.8 Volts on my meter. The battery was 4 years old and I wasn't the original owner. Tested it appeared to have at least one weak cell, so purchased a replacement and installed it, After a few turns of the key, it started fine and I drove it for over 200 miles without a hitch. On a whim had the Alternator checked when I arrived at my destination, regualter was not working correctly and under load wasn't charging the battery. Replaced the Alternator, suspect that probably poor regualtion wasn't helping the old battery either. Well another week maybe 10 days go by then it starts to do the same stall after 8-10 minutes of driving? I am getting annoyed.
I have run the vehicle in the yard for 30-40 minutes at idle, never shuts down. Since it is warmed up it doesn't stall going down the road, in fact it is so far not predictable enough to say it will occur every time. I have the majority of the enigne compartment cleaned up now, valve cover gasket is going to need replacement. I have not gotten over to the PCM to clean and inspect the connectors, that advise did sound promising, that will be a this weekend project for me. The cover screw length theory will also be explored since I will be in that deep. I have tested the Crankshaft Postiion Sensor (CKS) and the Camshaft Position Sensor (CPS) both appear to physically be fine and resitance checks are within the factory service manual. No amount of wiggle and jiggle will cause the vehicle to shut down on their respective wires. Reading the other posts of stalling I find similar but not the same symptoms. Fuel pressure is good at the plenum. My friends are joking that my slow methodical cleaning is part of the problem, removing all the dirt that was holding things together. I have not used a pressure washer to do the cleaning all with off the shelf spray cleaner and the garden hose to remove excess. Every cleaning session ends with starting the engine and letting it ilde for 15-20 minutes, then shutting it down and doing that again. So far not able to induce the stalling problem.
So just looking for anyone with some reasonable feedback as to their results from troubleshooting this sort of problem. Please don't just throw out a grocery list of parts that you think need to be swapped out unless you also deliver the said parts list for free to me, as that would be wastefull of our time and my money, I am seeking troubleshooting advise here.
If I offended anyone with that comment, don't assume it was directed at you personally. Thanks.
BTW - I will post the results of my efforts as they are available. Don't want to nick name my Jeep Picky Little Son of a B!^@h if I can avoid that!

ncsufan44

I am having almost the exact same problems with my 99 XJ. It is a 4x4 I6 4.0L. Most of the time it only hesitates while driving and is able to regain power, but occasionally it does totally shut down. I was told it was the fuel pump, but i find it hard to believe that the fuel pump works sometimes and not others. I am going to try replacing the spark plugs and wires. I have already checked the fuse and the relay and they are good. I want to try as many small and cheap fixes as possible before I have to drop the fuel tank and check it out. Hopefully we can figure this thing out.

sunny5280

Are there any codes stored? You mentioned P0135 which you alluded to applied to coils. However it appears to be related to the O2 sensors which I did not see in your list of things replaced.

I just recently went through a intermittent stalling issue on my friends 99 GC. While the symptoms you've described are a little different don't overlook the PCM. You mentioned you'd be inspecting it along with the connections. From my experience the PCM was filthy but the connections were fine. Nice and clean, no corrosion, etc. The PCM was replaced and, two weeks later, not a single problem with stalling.

Now I don't want to look at every stalling issue as PCM related but there's an easy, at least IMO, way to check. If the 96 GC provides the same code reading capability as the 99 GC you may want to see my comments on how I tested the computer. Might be helpful information for you.

Good luck.

buddyjaet

Well, Fuel pump comes up often, I put my pressure tester on the rail, solid 50 PSI, at idle, factory manual says 49 +/- 2 PSI. Rev the eingine and it never waivers from that mark. If the pump were failing then low flow should show up or low pressure as demand increased, I saw neither of them. The alarm and the PCM do have control to shut down the Fuel pump, but they would do that based on some other inputs or lack of. The PCM on my Jeep was very clean no signs of corrosion on any connectors, clean and replaced them all. I have since discovered the CAT is clogged up, in process of remove and replace at this time, only have weekends to do the work so slow going. The riddle continues, thanks for the response, we will figure it out just doing the troubleshooting versus throwing money at the problem till it runs again.

buddyjaet

NO I stated "OBD2 scan tool says P0351" but I could see P0135 as a misread.
You mention a replacement PCM for $160, do you have a vendor I could call to get that price? The usual sources start at $265 down here in LA (Lower Alabama) for one that also carries a warranty. Would you send a link to your post on PCM troubleshooting. I don't have a valid reason to suspect the PCM on mine yet. The PCM may be the root of the stalling, I just have not found a reliable troubleshooting method to verify it is the deffective part which is causing the stall. However, as I verify all the external inputs are working correctly and the wiring is not at fault, logical troubleshooting would lead to swapping it out. strange how the more I troubleshoot the system and clean and reconnect wires the more unreliable the problem becomes, yet it had not gone away.

sunny5280

Hmmm...I wonder how I messed that up as I copied it out of your post and posted it directly into Google. Anyway...

You can find my initial post here:

https://www.cherokeeforum.com/f5/sud...2/#post1921148

Along with follow up posts describing how I arrived at the PCM being the issue. While you don't have the exact symptoms I'm hoping the "test" procedure I outlined will help you diagnosis if the PCM is the issue (as it's fairly simple). This assume you can perform the test given you have a different model GC than my friends. I have a very high level of confidence this test can identify the PCM as being the issue or not. Enough so I ended up ordering a new PCM based on it.

I purchased my PCM at Autocomputer Exchange. I did have a slight shipping issue which they rectified even though they were not obligated to do so. Other than that I'm very pleased. They were helpful, courteous, price was right at $160 (looks as if the price is now $199). Unfortunately it looks like your model year is $299. However they sell on ebay and they're selling it for $189. Search for auction number 350453349105.

Good luck and let me know if there's any additional information.

buddyjaet

Okay, so who would beleive the catalytic converter guts had begun to meltdown. After the vehicle would warm up it clogged the exhaust. With the sawz-all removed the cat and Jeep fired up and ran great. Left the oxygen sensors plugged in so as to not trip that code. Darned if there were no stalls, no codes, ran as you would expect. So visit the local Autozone, pickup a replacement converter, funny the old one looked like it was home built! Installed the new catatlytic converter, clamped everything in place, (BTW - I think the bubba that did the converter swap before left off a hanger) fired it up and drove for over an hour without a problem, start and stop the engine for another hour or so, cooled it down and then idled in the yard to slowly warm it up and shut it down, never once a code, a problem just ran!
So my mystery was a combination of Deffective Voltage regulator, (replaced Alternator), a Dead Cell in my battery (replaced the Battery), and a dying POS aftermarket catalytic converter that was melting down and clogging the exhaust. PCM was just doing its job this time and shutting down the system due to other inputs. Well, now I am back to a small exhaust leak in the manifold to exhaust pipe gasket that will need to be replaced.

SOLUTION HERE: Clogged Exhaust System due to a deffective Catalytic Converter.

Now checking the VIN against the posted recalls, I still have an open issue with the PDC and Fuse Link to get the dealer to fix for me.

So thanks for the feedback and the resources, I am back to enjoying driving down the road again, for a while.