oi there ole matey..a digital vernier caliper is what I use, accurate to .0005", cost me $30, anyone that fits aftermarket parts without measuring them first is inviting disappointment into their lives

@ the OP, so the main ground locations are the two big studs near each other on the side of the engine block, each with a bunch of wires, you cant go wrong to check and clean them very well

The FSM does list all ground locations, reading the FSM is good practice, helps one nod off to sleep

Have you inspected the crank and cam wiring carefully to see if it is brittle or cracked ?

 

Yep, got one (different brand) for reloading. 3 rounds, 200 yds, 1&1/8" group. 130 yds, double lung, elk backstrap, YUMM !

Grounds @ coil cleaned, see above

Cam pick up, CSP replaced, and wires flexible, but connector saga continues, see above

Initial reply from AWG above "search the XJ archives for that code, there was a dude that persisted till the end with that code, was maybe a couple of years ago, about 30pages" How do I access XJ archives?

Thanks
goodyoleboy

 

You said vernier, which to me is the old calipers where you had to eyeball the lines and decide which ones lined up. I think I still have one somewhere from ages ago. I mostly use my dial calipers, or the digital. The cheap digitals just eat though batteries, whereas the real name brand ones don't.

 

Up near the top bar, click "search" select "advanvced search" put in P1391 as the search words, and u may be able to refine it by putting awg but i was not the author...I could not find the post I was talking off when I looked though



Yes, I have some, and had to use them recently when I misplaced my good one, and my cheap one had..a flat battery

I have to put my glasses on and remember how to read them, its easy to make a mistake unless you are used to them, the digital verniers are so handy I rarely use my micrometers

 

so i just searched again, using the exact method as shown in previous post and found the long thread...there are others to, P1391 seems a common problem

happy reading

99 PCM replace/update - Page 24 - Jeep Cherokee Forum

 

Thanks for the extra effort!
Probably helps when you know what you're looking for and how to navigate the software.
Looks like I've got my homework all laid out for me.

More to come.

Thanks
goodyoleboy

 

Dear AWG:

Just a cursory review of 4x4jeepmanthing trials tells me that operating the meters, oscilloscopes, etc required to wade through the wiring is FAAAR beyond my skill set.

All I understand how to do is follow the sequence of events leading up to the CEL illumination, look for what changed or what's different, and change the most likely parts.

I chose this type of vehicle because I had heard of its reputation for reliability and it only had one computer instead of three.

The jeep only has 153K miles, hasn't been off road, but it has been neglected. When I drained the auto trans "fluid", it looked like thin chocolate pudding.

Despite its neglect, the jeep ran fairly well, but not to where I could trust it. Wanting to be proactive, rather than waiting for each part to fail ( requiring diagnosis at $125 to say hello) I replaced the coil, distributor, pick up coil, rotor, cap, wires, plugs, entire exhaust system incl both O2 sensors, and added a can of BK44. I have other sensors (TPS,etc) ready to go, but have waited to install them not wanting to confuse the problem further by introducing additional variables.

When the CEL came on with the P1391 code ( knowing / hearing of the propensity of the CPS to fail) I planned to replace the crankshaft position sensor ( on back order) as soon as it arrived. Unfortunately, the connector was different which required my resorting to the local auto parts store for the one with the correct connector configuration.

The connector to the CPS was suspect because the plastic snap connector was broken off and the two pieces were glued together. I cleaned it thoroughly and reinstalled it , (see saga above). I've since learned that the "old" style connector is no longer made. see saga above.

I've since received that correct connector and plan to install it and the CPS that matches it, but if the connector is not the problem it seems unwise for me to delve into the wiring.

Are there any other steps someone with my limited electrical "skill set" might take before throwing in the towel?

Than you again in advance for your patience and tolerance.

goodyoleboy

 

Please elaborate on "re-indexing the distributor" referenced in other questions.

Thanks
goodyoleboy

 

if you didnt have that code before changing the distributor put the old one back in. the aftermarket ones are always off a little bit. could also try rotating the distributor gear 180 degrees.

 

Is this the re-indexing process referenced above.

The old one was WAAY loose and sloppy with an oval rather than round orifice for the shaft.

Unclear to this old folk how the engine would run fine with the timing 180 degrees out. Please explain or refer to alternative data source.

Should I be abandoning the search for grounds (above) and refocusing on the distributor?

Thanks
goodyoleboy

 

I have a 96 xj that had the same problem. Distributor bearings were shot and the shaft had a lot of play. Engine would cut out while driving, but never stall out. Had no codes, only found it after pulling the cap and noticed the rotor looked askew. Put an aftermarket distributor in, it ran fine, but threw a po1391. Checked continuity, voltage, cam, crank sensor, coil, ect... everything tested fine. Pulled the distributor out to get a closer look. Noticed the gear on it vs. the gear on an oe take off part were not installed the same, the hole that the pin goes through and the cut of the teeth are not symmetrical. The distributor might have had the gear installed 180 degrees out, causing the reluctor to pass through the cam sensor too late. When the computer doesn't get the right voltage from the sensor it triggers this code.... I returned the reman one and put a junkyard distributor in. No more code.

 

You wouldn't be putting the timing 180 out, that gear being 180 out causes the timing to be out a few degrees. That gear can go on the distributor two ways. One way is perfectly in time, the other way is just a little out and will allow the engine to run, but throw this code.

 

Wow !

Who knew?

Looks like I get to tear it apart tomorrow.

Thanks
goodyoleboy

 

So I rotated the distributor gear 180 degrees, put it back together, and it started right up! Took it for a ride ( about 25 miles) and no CEL! The last time it was on within less than 8 miles. I’m going to try it again tomorrow morning, but I’m cautiously optimistic. Cue the Twilight Zone Theme.

But I'll still keep the spare CPS and connector in the jeep just in case.

After a brief rest, I'll tackle the poor gas mileage.

Thank you all for your help.

goodyoleboy

 

Wait a minute!!! So you didn't rotate the distributor 180, you took the gear off the shaft, rotated it 180, reassembled, re-indexed and now it runs fine?

This was a "new" distributor?