P1391 code drama

M

mikejengineer

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Joined
Dec 28, 2019
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ALABAMA
I've spent about 8 months (on and off) trying to get this 2000 TJ (86K miles) to run properly. I'm the original owner. I have read a lot of threads here about P1391 codes. Without going thru a litany of trials, please know that every sensor I can think of has been replaced with Mopar or best quality available parts. Sometimes twice. Camshaft position sensor (including geared sending unit -properly installed at TDC). Crankshaft sensor. Throttle position, Air flow, plugs, ignition rail bar, 02 sensor, replaced the throttle air valve and cleaned the throttle body (was dirty). I've been working on cars a long time - and recently did some work replacing the A/C compressor on the TJ with no issues. I'm not a professional mechanic.

The short(er) story
The TJ idles rough. Throws a P1391 code consistently. By rough, I mean she starts quickly, idles for about a minute and then starts an intermittent "grumph" that cycles perhaps every 20 seconds.

I can rotate the camshaft position sensor / send unit slightly to the point she idles smooth but will die immediately under load. When warm, I can rotate the same unit opposite direction (slightly) to where she runs properly but idles poorly, dies and throws P1391 code.

An I missing something regarding ignition timing / advance?

I have not checked fuel pressure but the fuel pump is not that old.

I'd appreciate any insight members might have on this issue. I do miss driving her.
Thanks
 
I just went through a camshaft position sensor P1391and fix on my 2004. In my research, I discovered that there are 2 different sensors. I think the same one was used from 1997-2004 and then a different one was used from 2005-2006) Since you had the OPDA ('geared sending unit') replaced, I wonder which sensor you have?

If you still have the older style sensor, on mine the magnet in the center of the sensor had completely detached. I super-glued it back on and cleaned the steel part on top of the OPDA that spins around and that fixed my issue (I ordered a new one that hasn't come yet, so I'll be replacing it soon).

If you have the newer one, I wonder if the PCM from your 2000 is compatible with it?

If you can, please post photos of your sensor (on and off of the OPDA).
 
Thanks for the respondes

Very yes. Fuel pressure check would be smart. Will do

RMETeeJay
Thank you. As I was digging around the posts I saw your previous writeup and photos. It reminded me of how the CPS sensor housing small housing bolts lie perpendicular to the engine block. I went thru the procedure, checking TDC and aligning the oil pump slot at 11 o'clock position. The OPDA did drop right into place but the bolts on the CPS were not perpendicular. They are rotated slightly clockwise at perhaps the 1 o'clock position. I didn't give it much thought at that moment but I may have missed my proper install position.

So today I'm going to re-do the OPDA install and recheck the throttle body. I'll see if the CPS sensor cap mounting bolts will align correctly. I'll take some before/after pictures and if this clears things up, we'll have some photos for the next shade tree mechanic who makes the same mistake.

Thanks
 
mikejengineer said:
Thanks for the respondes

Very yes. Fuel pressure check would be smart. Will do

RMETeeJay
Thank you. As I was digging around the posts I saw your previous writeup and photos. It reminded me of how the CPS sensor housing small housing bolts lie perpendicular to the engine block. I went thru the procedure, checking TDC and aligning the oil pump slot at 11 o'clock position. The OPDA did drop right into place but the bolts on the CPS were not perpendicular. They are rotated slightly clockwise at perhaps the 1 o'clock position. I didn't give it much thought at that moment but I may have missed my proper install position.

So today I'm going to re-do the OPDA install and recheck the throttle body. I'll see if the CPS sensor cap mounting bolts will align correctly. I'll take some before/after pictures and if this clears things up, we'll have some photos for the next shade tree mechanic who makes the same mistake.

Thanks
Click to expand...
It helps if we use the right terms to keep folks all on the same page. You are working on a 2000. That year runs a camshaft synchronizer that plugs into the hole in the block that the earlier distributors and later OPDAs drop into.

If I was having your issues, I would find someone with a Chrysler DRB to set the timing on the camshaft synchronizer after it was installed. They have a range they will compensate for it being out of time that is about 10 degrees either side of 0. Wear in the gears will cause issues if it is right at the edge of the limit.
 
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After I exhaust every possible option "NOT being a mechanic" I bail & take it to the dealer ! Many times it winds up cheaper in the end as they diagnose it faster & correctly, therefore eliminating a slew of guessing & unnecessary parts.
 
Many people having this code, did the same as you, replaced every sensor under the sun, multiple times even. Much of the time it was a broken wire. This can easily be ruled out by doing a continuity check and see if there are any broken wires in the harness :)
 
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I went thru a situation recently with the TDC setpoint on my 99 and it was not until I physically confirmed TDC with the position of the piston did I learn the balance pulley had spun off center so you may want to confirm your TDC.
 
Well, part of the trouble was my fault.

Last time I did the ODPA replacement procedure, I was rotating the engine to TDC in the wrong direction.
This resulted in an install looking like this

20191229_101552.jpg


Note the position of the small bolts on the sensor cap


Repeating the procedure rotating the engine in the correct direction to TDC (clockwise) resulted in an install that looked correct.

20191229_120356.jpg


The CPS cap bolts look much closer to their original position.


Jeep runs a lot better but I still have some issue with a periodic "grumph" in the idle.

I think having a dealer diagnostic is a good idea. I'll update this when I get that accomplished.

I need to research spark plugs.
I think I have Champions in there. Maybe a better plug ( NGK ZFR5N ?)
would be helpful.

Anyway - if the install looks rotated clockwise, it may be that you reversed rotation when you were trying to find TDC

More later. Thanks. And keep the ideas coming. You guys give excellent advice.
 
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