jon-d

on the way to work this morning the engine seemed to backfire and just sputter out but as I coasted to the shoulder it restarted (without using the starter) and off I went. seemed to run normal all the way to work. I recently changed out the cap/rotor/plugs and cleaned the carbon out by using water. but that was about 200 miles ago so I don't think I messed anything up there. I don't want it to happen while I am 100 miles from home in the middle of no-where, any suggestions on where to start troubleshooting?

Bustedback

I can only throw out a guess, but I would suspect the crank sensor, or an electrical system issue.

jon-d

is it common for a crank sensor to be intermittent before failure? is it worth replacing at this point or should I just leave it alone?

jon-d

...or possibly injector issue?

jon-d

just to circle back to this yesterday my jeep threw out a P0351 and a P0420 code. engine seemed to be running fine even with the codes. did some research and it appears my symptoms and the code point towards the ECU as the problem. apparently the solder goes bad just like with our headlight switches. i took mine apart and the joints tested out good but i went ahead and applied heat to the connections to see if that cures the issue. the ecu appears to be a used one (by the markings on the outside) and two of the internal connections looked like they have been resoldered (looked new compared to the others). so i will run it for awhile and see if my intermittent problem returns. hopefully all will be good.

jon-d

Here are some photos.

jon-d

cant really see the solder joints but the connectors are at the top of the green card shown in the first photo. i saw some replacements on flebay that will program to your vin number so if this does not work out i will pick up one of those.

jon-d

well crap. on the way to work this morning the jeep started dying so I pulled off the freeway where it completely shut off. this time I had to crank it over a few times to get it to start. no codes either. I was able to make it to work without issue after it started.


I really hate these intermittent problems due to the difficulty in troubleshooting. I am thinking of replacing the ECU since the symptoms seem to point in that direction. it appears the prior owner had replaced the ECU so I question if he had the same problem and thought a new ECU would fit it just like I am now, or he did have that problem and the replaced ECU fixed the problem until now.

Willys55

did you check the crank sensor and it's wiring?

jon-d

I have not checked the crank sensor yet. I have taken the jeep on some pretty rough trails and it has not cut out indicating that a loose wire may not be the issue. what is the procedure to check out the crank sensor?

jon-d

perhaps I should back up a bit. besides the crank position sensor, what other components will tell the PCM not to run the vehicle?

dave1123

I just when thru this with my 2000 WJ. It would shut off randomly like I turned off the key and it didn't matter when or when it was, idling at a light or driving 55. It was also idling low and rough. Some times it would start itself if I was still rolling, but if I was stopped, sometimes it would fire right up and sometimes not. I figured it was a message that I had almost 200K miles on it, so I changed the CPS with a Mopar part. It's been running fine ever since. The TPS started screwing up about a month ago, but that threw a code.

BTW, people told me the CPS won't throw a code, but my WJ will. It can't be read with a scanner, but will set a P0320 on a key test. Also, the TPS problem was just after a Seafoam application.

jon-d

Ok, so I ordered an OEM CPS should be in next week. I took a look at the one thats in there and it looks origional so I am hopeful the replacement will cure the issue.

97grand4.0

I assume we are assuming the fuel pressure is ok.

jon-d

Yes and that's a good question. I checked fuel pressure a few weeks back and it was holding 48 psi with little bleed off. I can also hear the pump running while attempting to start it last time it died.