03 WJ engine split second cut out, never stalls
 

Hey Everyone,

I am having a recent issue with my 03 WJ with 4.0 motor in it and around 165k miles. It is completely stock. Lately while driving the jeep will suddenly cut out for maybe a half second at most but never stalls. It has been happening and idle all the way up to highway speeds. No check engine light or codes. It almost feels like the transmission slips but when it does cut, rpm gauge and speedometer drop fast (speedometer will drop 15mph on the gauge but only cuts out for split second so impossible for me to slow that fast). After it cuts, everything goes back to normal. It happens both with cruise on and with cruise off. If cruise control is on and it does it, it will kick off cruise and shut the light off on the dash for cruise. I am guessing that this is the ignition cutting out but have no way to tell. TPS sensor was replaced and I am suspecting the CPS but I have not changed that out. One thing to note is the battery is about 7 years old but will still start the Jeep at the -25+ mornings we have been having the past few weeks. Slow crank but starts. I doubt this is a battery issue. I have searched all over for the same symptoms on this forum as well as others but everyone else's jeep engine completely stalls and has to be restarted. The engine has never stalled once yet. Mine just cuts out for a half second and goes back to normal. Any help will be appreciated! This is driving me nuts.

Very similar symptom on our HellKitty ZJ. Cut out but only momentarily.
Was failing CPS.
New one in, corrected that problem.

Ok I figured as much. I ended up ordering an oem mopar sensor. Should be in stock early next week. Hope it does the trick.

Well I replaced the crank sensor with a mopar OEM sensor and it still does it. It kicks off cruise light when it does it with cruise on. Also at idle I will get a random idle surge. That too is split second. Any thoughts???

This issue may be getting slightly worse now. Anyone else have any ideas?

In case anyone has these issues as well, I replaced the PCM and it fixed the issue. It's only been a couple days since but appears to be the fix.

Problem solved.
 

Well I guess I get to join this club as well, I have the exact symptom as VIANE describes at the start of this thread. My Jeep is a 2003 Grand Cherokee 4.0 liter with 80K miles. I replaced the PCM today and took it for a drive, no help, if anything it made it worse. To the point that it completely died twice in 5 mile stretch. Either the replacement PCM has same issue but worse, or the component that is the problem is getting worse. I guess I will try crank position sensor next.
I know this is a old thread, hoping somebody has found the answer to this problem. I replaced the battery just to rule it out. When this started I was on a trip, It bucked it's way home, almost 800 miles. But now I would not leave town in it.
06/22/22. I have replaced the crank position sensor, cam position sensor, throttle position sensor, and tried another PCM. Nothing seams to be making a dent in this problem.
I noticed when replacing the throttle position sensor when sliding the connector plug on sensor there was very little resistance making me think the female connectors lost their spring tension,
so tonight I took the plug apart and squeezed the female receivers with needle nose pliers. Went for a drive and went over 30 miles with and without cruise on, no stumbles.
Then at 55 MPH I floored it and ran up to 80 MPH and it stumbled one time and turn off cruise control. Still may be the TPS plug. Looking for replacement to solder in.
Anybody else been this deep into the this issue?
07/28/22 Since last post I decided to drive the Jeep locally till it failed to run, that day finally came. Died of a bumpy road close to home, restarted and would idle and rev up in park, but as soon as it put in Drive and I pressed on gas pedal it would die. Pulled it home and tried backup PCM to see if that changed symptom,,, no change.
I tried re-seating all the plugs under the hood, no change. Wiggled wiring harness around many times, it went from no starting to start and idling.
I determined that the problem was in wiring harness that runs around the back of valve cover and feeds the injectors and intake sensors. I pulled the harness from behind valve cover and found on the underside a hole wore through the sleeve on the harness. Turns out there is a valve cover bolt head on back that the harness sit on.
This Jeep only has 84 thousand miles, so it is well worth fixing the issue.
After close inspection I found 3 wires with insulation wore through exposing the copper wire, that was grounding out on valve cover bolt.
I cleaned the wires, wrapped them with contact tape, re-wrapped harness with 3M high temp tape, then sleeved the harness with heavy heater hose. put everything back in place and took Jeep for a long drive. No more issues, runs great again.
I am attaching pictures to show progress of finding and fixing issue. Hope this helps other people.
This wiring harness is about $900 from Jeep dealer, that does not include $100 per hour shop rate to find the issue and replace harness, I feel certain that a dealership would not repair the damage wires.
https://cimg1.ibsrv.net/gimg/www.che...6a4f40ae84.jpg
Wear through harness casing.
https://cimg5.ibsrv.net/gimg/www.che...064abcfd23.jpg
Valve cover bolt that harness sits on.
https://cimg5.ibsrv.net/gimg/www.che...18e1cecfd0.jpg
Three damages wires exposed.
https://cimg3.ibsrv.net/gimg/www.che...f9a97d7f00.jpg
Wires wrapped with contact tape.
https://cimg4.ibsrv.net/gimg/www.che...cf4c5f2cac.jpg
Harness wrapped and sleeved with heavy heater hose.
https://cimg7.ibsrv.net/gimg/www.che...c9a8f6eb69.jpg
Harness back in place behind valve cover.

My 1998 Grand Cherokee 4.0 used to have that brief glitch going over rough pavement. The tach would flutter and there would be a momentary loss of power, then it would resume again. The check engine light didn't come on. It was the ECU. Apparently, these ECU's have low quality solder joints which crack or separate over time. So, the connection is OK until it gets a shake or it gets very cold. I found a guy on Ebay that opens these up, removes the potting (some anyway) and re-solders the connections. He did it on an exchange basis using the ECU part number to be sure the replacement was compatible. He claimed to test the repaired ones. It worked fine after that.