Jeep "FLU" 2000 Cherokee Sport 4.0 CA Emissions

2000 Cherokee Sport 150,000 miles: Jeep runs fine for about twenty minutes give or take, then starts misfiring, sputtering, stalling, sometimes I turn ignition off and immediately back on and I am fine for a few minutes. Codes are loss of ignition primary signal, loss of camshaft crank signal and of course various accompanying misfire codes. I have replaced crank and cam sensors, oil pump drive housing, removed the entire engine harness, inspecting cleaning, re-taping, and reassembling every connector with dielectric grease. I recently (within the year) have replaced all six injectors, coil, plugs. I have "seafoamed" through the throttle body. My next stop is computer or the flexplate. Internet research has been inconclusive other than ZJ's seem to have a similar problem but opinions differ as to the primary cause. PLEASE HELP!!! It drives fine usually just long enough for me to get to and from work, but it is driving me crazy. I had a mechanic at the auto hobby shop (Im in the military) look at it with me and he's stumped- but says there is only a 1% chance that it is the PCM. The sensor voltages and wiring test fine, they are cheap aftermarket sensors- I have ordered mopar ones just to eliminate the possibility before I drop the tranny or replace the PCM.
Anyone ever actually resolve this issue?

Should have also mentioned that I "resynchronized" the oil pump drive housing when I replaced it (toothpick method).

I bet you've already done it but maybe check/clean all your grounds?

I have recently, the block grounds are good for the wiring harness, I'm going to do the chassis, replace the braided, and replace the batt. cables.

The symptoms point to thermal failure of a sensor.

Follow the Check Engine Lights codes, your Jeep is trying to tell yo what is wrong.

Post the exact code numbers here.

Use genuine Jeep sensors. Cheap crappy "Lifetime Warranty" parts are often out of specification or even failed right out of the box. Many times they have a short service life before they fail. Lots of threads note intermittent or random issues that were solved by replacing crappy sensors with genuine Jeep parts.

Have you tried O2 sensors? Sounds like maybe it starts acting up once it falls out of closed loop mode and starts listening to all the different sensors. I had similar symptoms when I had an issue with my upstream O2 sensor. Turns out it was some frayed wires, a blown O2 sensor fuse, and shorted out sensor. I believe your 2000 has two upstream if it has pre-cats and only one upstream if it has one cat. I could be wrong on that though since I am not fully familiar with the emissions systems on the 2000-01. I know it is a long shot since you don't get a code for that but hey you tried everything else it sounds like other than replace the computer.

After confirming good quality engine sensors are being used, as suggested, testing or replacing the O2 sensors would be the next step. Normal service life of an O2 sensor is about 100-150,000 miles. Signs of O2 sensor failure include bucking, stalling, backfiring, sputtering, and/or an unexplained 30-40% loss of gas mpg's

Codes are:
P0353, Ignition Coil #3 Primary Circuit
P0352, Ignition Coil #2 Primary Circuit
P0351, Ignition Coil #1 Primary Circuit
P1391, Loss of Camshaft Crank
I replaced the Ignition Coil twice earlier this year, First time with a cheap one then with a Napa. Do coils intermittently fail? I have always thought of coils as either good or bad, no in-between. I guess I am also assuming these are caused by the P1391 code. I replaced the cam sensor with a mopar. I have the mopar crank sensor (haven't had a chance to put it in yet), and I have all four Mopar Oxygen Sensors on order. I WILL NEVER BY A NON MOPAR PART AGAIN> The cost of re-replacing everything, just to eliminate the possibility of a bad part has been...educational.

oh, and the oxygen sensors cost almost four hundred dollars! Almost as much as the computer, but I figure with 154124 miles, its about time anyway- so still money well spent.

I'm posting to make sure this is in my subscribed threads...

Try these:


P1391 Intermittent Loss of CMP or CKP. Loss of the Cam Position Sensor or Crank Position sensor has occurred.

P1391 – Possible symptoms:
(1) random misfire/stumble/stalling, usually over bumps or right turns and reverse.
(2) shorted out the Fuel pump/ecu constant power wire and every time I'd go over a bump it would pop the fuel pump fuse and kill the motor.
Partial Fix:

Clean/replaced engine GROUNDS! - Found braided ground strap from valve cover to firewall touching metal brake line on firewall and "shorting out" !!!

-Rerouted ground strap away from brake line
Real Fix #1:

Found an engine wiring bundle at firewall was wrapped around the backside of the fuel-rail. The fuel rail had punched through the corrugated plastic wire and black tape covering also worn through... dug deeper... "3" three wires in that bundle, right at the same spot, had the insulation worn through just enough to barely expose the wire. It all made perfect sense... every bump or right turn was enough to touch these wires to the fuel rail causing a short i.e. intermittent loss...!!!

-Wrapped the wires individually with tape, wrapped the bundle with tape, replaced plastic protector and wrapped with tape... Pulled the bundle up and away from fuel rail secured to the other wire bundles on the firewall.

Real Fix #2:

Timing is off. Re-index distributor or Cam Sensor per the FSM instructions, or replace faulty parts.

Google SCAN TOOLS, O-SCOPES AND TOOTHPICKS

A mis-indexed distributor/cam sensor may exhibit surging, light bucking or intermittent engine misfiring. This will most likely occur when the vehicle is at operating temperature and under a light load at approximately 2,000 rpm. This condition may be caused by a mis-indexed distributor/cam sensor.

The factory procedure must be used as outlined in the service manual or the toothpick webpage.

maybe there is a pin in one of the electrical plugs that is opened up to much

I'm gonna say you are still unsync'd, due to the 1391 and misfire codes. Did you make sure you had #1 piston at TDC at the end of the compression stroke?

I was thinking about both of these. I am changing the crank sensor today, will also tweak the connections to close them up a little. I was thinking about bringing to the dealership to hook to DRB to sync. On the online instructions it says if you sync with toothpic you don't need to however my FSM says do that and then still fine tune with DRB.

Re: SOLVED Jeep "FLU" 2000 Cherokee Sport 4.0 CA Emissions

SOLVED~
I will never buy non Mopar parts again. I was somewhat skeptical on this advice-I had replaced the camshaft and crank sensors twice with cheapies from a1 auto parts on line and autozone respectively. My thoughts being how could multiple new parts from different sources be bad??? Well, after replacing four oxygen sensors, and on the verge of buying a computer, I took the advice of remediating everything to factory Mopar...I changed each sensor individually and drove for a while to determine any change and finally the last sensor (due to it being a pain in the a**) was the crank sensor and after 50 miles so far with no bucking or stalling or limp home mode, I'm convinced. The crank sensor was my least suspected as well due to being told several times that it is a simple hall sensor, has signal or doesn't and when it doesn't- no start. That was not my symptom.Hastaarty:

Way to stick it out