P1391 Code & Low Power

wigsajumper

TJ Enthusiast
Supporting Member
Joined
Sep 17, 2017
Messages
347
Location
Maine, United States
A few weeks ago on the way to work the CEL came on. Pulled the Code and it was p1391. Was having significant power loss on the way home. Jeep was struggling to climb hills. I ordered both MOPAR sensors and replaced both. The code cleared while I was working on the vehicle because the I disconnected the battery.

After replacing the sensors the Jeep still is running rough. When attempting to climb a hill I can hear a tap or thunk which goes away if I don't accelerate hard or keep the RPMs low. It seems to be idling rough.

No codes have come back. I have only driven the Jeep about 4 miles since replacing the sensors and let it idle today while clearing snow from it. How long does it usually take for the ECU to register issues with the Camshaft and Crankshaft sensors? I think the FSM said 2 cycles.

Next step check wiring harness? Coils? Sparkplugs? Verify TDC?

Link is to a video of the engine running it has been idling rough since the changing the sensors.

https://photos.app.goo.gl/xzDzj7vfcVMe6FSD8
 
Do you hear a popping at the exhaust pipe ?
I would pull the spark plugs to see if any of them have excessive carbon build up.
Sounds like a problem with a lifter, push rod and rocker arm which will require you remove the valve cover to look for loose rocker arm(s).
IF you have a bad lifter this may have also damaged the camshaft lobe the lifter rides on; which will require you to replace the camshaft.
Lets hope that noise is not the other problem that I am thinking of....
 
  • Like
Reactions: wigsajumper
If this is a new sound I would focus in on the camshaft synchronizer assembly. With the engine running, place your hand on top of the synchronizer assembly and see if your can feel feedback that corresponds with the ticking.
 
  • Like
Reactions: wigsajumper
In Dec 2019 there was a member with a similar issue; here is what resolved his problem.

https://wranglertjforum.com/threads/p1391-code-drama.30013/
I don't believe OP is at this point yet. So far he's only replaced the sensor.

The camshaft synchronizer on the 2000-2004 TJs is different that the OPDA on the 2005-2006 TJ but they both have a gear that the camshaft turns. Granted I never had this issue with my 2001 TJ but I did have an issue with the OPDA making a similar knocking sound on my 2005 LJ.

https://wranglertjforum.com/threads/oil-pressure-sensor-ticking.18631/
 
  • Like
Reactions: wigsajumper
Was the engine fully warmed up when you captured the video? It sounds like a noisy lifter to me (I get the same initially for cold starts).

Next step check wiring harness? Coils? Sparkplugs?
Yes, you should get your ignition system into a known good condition. When were your spark plugs last replaced/checked? If you need to replace them, read this first:

https://wranglertjforum.com/threads/what-are-the-best-spark-plugs-for-my-jeep-wrangler-tj-4-0.4196/
Once you confirm your ignition is good, move on to fuel delivery next (check pressure).
 
@RMETeeJay The engine was warm. By the time of the video the Jeep had been running/idling for almost 45 minutes while I was checking sensors with Torque Pro app and cleaning snow. It has been a couple of years since the spark plugs had been changed. Since it was suggested I check them earlier in the thread I figured I might as well change them also. Thanks for the link.

@AjRagno checked the camshaft sensor like you suggested. I didn't notice anything when I was touching it except for engine vibrations.

@CharlesHS Here is what the exhaust is sounding like. Is that the "Popping Noise" you mentioned?

https://photos.app.goo.gl/45Ptc5r9yLSiqzxSA
 
Take it out and get the RPMs up to see if you can trigger a code again. This code can mean a lot of different things, so if you search for it online, you'll find a ton of different stories.

To start, I'd make sure you have the right plugs in and that each coil pack is firing correctly (with a test light).

Here's my P1391 story: I have the same year as you, and when I got this code, it was related to the OPDA failing (which isn't as common for our year as it is for 05 & 06 TJs). I replaced it, but couldn't clear the codes until I fully reset the PCM. Here's my recap in the thread with instructions on how to do a full reset:

https://wranglertjforum.com/threads/any-benefit-to-resetting-pcm.15762/post-491275
 
Update - Just got the LJ back from my mechanic after doing a frame repair. While he had it he looked over the motor to see is he could find what the issue was for the code and running rough. Seems my ignition coil pack was bad. Engine was only running on 4 1/2 cylinders.

Once I get it inspected will take it for a longer drive to see if that was the fix. Mechanic is only 1 mile from the house but it ran great even accelerating up hil.