jjdunning

First off, I think I've read every shred of advice when it comes to this nightmare I find myself in. So, thank you in advance if anyone has any new advice for me.

Some background first. The XJ is a '99 Sport, 4.0L, Auto, 157k, 3" lift, etc. etc.

About a year ago it left me stranded in a parking lot, cranked all day and no start. I'm an average mechanic, I know the basics. So After work I bought a tune up kit from autozone. Plugs, wires, dist. cap, rotor, coil pack, and an air filter. After changing all the parts in the dark and cold, it wouldn't start, was jumping it off my other car. I had left the coil pack flopping on it's own, and thinking that if I had it towed to a garage, the mechanic wouldn't know what was going on, so I tool the time to bolt it up where it was supposed to go. As a last ditch effort, I tried to jump it again and it started. So I left it overnight in the same parking lot, and the next day it started and drove normally. I went to the parts store for a battery/charging system test, battery came back bad (of course) but the alt. was fine. So, in goes a new battery. Two days later, in my driveway, same thing. Cranks all day and no start. CEL light is on. Can't remember when it came on.

This time it gets towed to a garage. The pull a code, P1391, and replace the cam sensor (under the dist cap) and it runs and drives, no code, and I get a Mass inspection sticker to boot.

The same time, my AC compressor decides to eat itself, so the garage removed and replaced with a bracket to hold the pully, and I go without A/C from then on. At the same time, I get a new radiator, some other odds and ends, and I think all is well.

I pick up the truck from the garage in the aftermath of the nasty snowstorm we had on October 2011, power was out for a week, and on the way home from the garage the CEL comes back on. I borrow a OBD scan tool and pull the same P1391 code. I do nothing for quite some time because it's running fine, and starting every time. Strange thing is, every so often the CEL would go off, then randomly come back on.

After that, my mother in law borrows it for an afternoon. I get a cryptic text later on letting me know that the Jeep is leaking water. Confused, I get home to find a puddle of coolant under the Jeep in my driveway. Upper rad hose spilt. Off to the parts store for a new one and a gallon of coolant. Stoopid me, I should have bought them both, because later that same week the lower ruptured and before I could stop and shut it down, the temp gauge spiked and the red idiot light on the dash came on. So, new hose, more coolant, and I'm back in business. Several months later, temps drop, it gets cold, and I have no heat. Attempt a reverse flush on the heater core and flush all kinds of nasty crap out of it, now the heat will melt your face.

Still plagued by the CEL light however. Admittedly, I have not scanned it in a few weeks. I had to return the scan tool. However, before I did that I replaced the crank position sensor on the bell-housing, checked, thread locked, and tightened the flex plate bolts, and replaced the cam sensor under the dist. The Crank sensor was a Mopar part from the dealer, the Cam Sensor was an Eichlin from NAPA since the dealer was out. Used dielectric grease on all the connections. I've flashed the PCM a couple times, each time the light stays out for the initial start-up and test drove around the block, and sometimes it'll even stay off for the entire next trip. Always comes back though. Lately, it has never shut off on it's own. It's been on for a long time now. Reason this is getting more pressing is I was due for my annual donation to the state of Massachusetts for a sticker.

The thing that really makes me crazy is I've driven from Western MA to the Berkshires; Boston a couple times; Princeton, NJ; Philly; Greenwich; New Haven, and 20+ miles everyday back and forth to work. Jeep runs pretty good. Not great, because it's a 157k mile Jeep.

So, sorry for the long post, but I'd rather get everything out on the first try. Experts have any advice? What have I missed?

PocketsEmpty

Check out this thread over at Jeepforum:

http://www.jeepforum.com/forum/f11/p...sensor-828759/

Sounds like either the replacement cam or crank sensor is faulty. I'd start with the cam, since that part isn't from the dealer.

jjdunning

Thanks for the reply. I'd tend to agree with you about the sensor, but two bad sensors out of the box seems unlikely. Also, I understand NAPA is a better sensor than some of the other auto part stores supply. Costs as much as a dealership.

I've also read through that post on jeep forum, several times. Thanks for the link anyway. This weekend we're expecting a snowstorm again, so I'll go back through the wiring again and look for loose or broken wires, and I'll clean all the grounding points too.

As a side point, did another 200 mi round trip yesterday with no problem. Just an annoying CEL light.

ordnance

JJdunning,
Did you ever resolve your P1391 issue?

jjdunning

Hey,

I have not. I haven't done a lot of checking lately as I dive mostly in CT and they don't care that I have an expired MA inspection.

It's been running fine until recently, started idling rough and had a couple flat spots in the rev range. Also developed a small exhaust leak which shouldn't be related but is equally annoying.

I'll throw some plugs, wires, coil pack, and a cap and rotor into it to see if it comes back. If not, I'll go the whole distributor route as that's the last things I've yet to do.

Sorry, let me know if you have any success.

-jjd

ordnance

JJD,
Thanks for the update sorry to hear you have not found the issue. At the time I posted I was hoping you might have some Insight on how to resolve my P1391 although my symptoms were slightly different. However I ended up finding and resolving the problem that same day.

Vehicle: 97 XJ, 4.0, AW4, 4x4

Symptoms: Intermittent P1391, P0340; P0320 one time, P1391 experienced about 10x more than the other two. I could not replicate the codes by just revving the engine I had to be in drive and most of the time at or above 2000 rpm in top gear. I did experience some bucking but it was very infrequent it was also at or above 2000 rpm when it occurred, but for the most part the XJ ran flawlessly.

Troubleshooting: Replaced CKPS, no change; disconnected clockspring, no change; replaced TPS, problem went away for two days then returned; replaced CMPS, no change. All sensors were mopar parts. Frustrated I thought about all of the stuff I replaced over the last two weeks and realized that the only time I saw an improvement was when I replaced the TPS. So I wiggled the wiring to the TPS in an attempt to replicate the P1391 no joy code would not get thrown. So then I asked myself what did I move when I replaced the TPS, and that took me to a large harness behind the TPS that has the wiring for the CKPS, and CMPS this harness also ran over the fuel rail. Upon inspection of this harness I saw that the plastic looming over time had broken away and the wires were sitting on the fuel rail. I inspected the wires and saw that two of them had nicks in them but they did not look deep enough to be causing s problem. I then looked at the wiring for the CMPS and the same color wire was at the sensor that had a nick in it. I then tested the sensor end to the insulation nick. Sure enough the nick in the insulation was an open circuit to the CMPS.

Repair: Six coats of liquid electrical tape over the affected wires. Rewrapped the section of harness in dry electrical tape, re-loomed the harness and secured with friction tape.

Theory: This problem would not have been found without visual inspection! Meggering, wire continuity testing, wire end to end, or end to ground would likely all yield
satisfactory results. Reason: The wear the wiring insulation occurred/ occurs when the engine is operating under load and when the engine is operating under load the engine is in a slightly different location than when idling or revving in neutral. This alignment change allows the insulation breach to direct short or take the path of least resistance and jump to ground resulting in P1391.

Anyways, this is what I believe happened in my situation hopefully it can help someone else.

Scott