Code P1391, misses at operating temperature, runs perfectly at startup until warm

Thanks Joe. I will have it scoped, but the shop has such a backlog it may be a couple of weeks.

I agree the symptoms point to faulty CKS, but that would mean that I've been issued two faulty new sensors. Also, I did reinstall the old (original) sensor, and it performed in the same fashion (faulty after motor came to operating temp). This all occurred after new distributor was installed.

Is there any chance the cam sensor(s) could be causing this? P1391 refers to both (cam and crank) is the main reason I ask, and the fact that I replaced the distributor which is where the cam sensor is located.

Bottom line I need to get it scoped after it gets heated up and mimics symptoms. Take the guessing out of it. Appreciate your input. Wilson

I have it scheduled to be scanned on 8/12. Hope they can find the issue. I'll report back as soon as I learn. Thanks.

Could it possibly be my wiring harness, and how would the location be detected for this particular sensor? No other circuits are malfunctioning. I did notice yesterday that it drove fine for over an hour, restarted fine until I switched my air conditioner on. It immediately started to miss when the A/C was turned on, and it never recovered even with the A/C turned off. I'm going to try the same test today leaving A/C off and see how long it drives without missing. Ever hear of that? A/C causing overload to crank sensor or cam sensor? Still haven't ruled out faulty cam sensor in brand new distributor. The scan I have scheduled on 8/12 will tell us which sensor is faulty since P1391 is not specific to which sensor is failing.

I do have an additional question(s). One that I've asked auto mechanics who say the cranks sensor does not need any relearning steps once installed. Are you aware of any relearning steps required after installation and before operation for a new crank sensor? How about the new distributor where the cam sensors are located? Any relearning steps required when new distributor installed to sync the cam sensors?

Update: scratch the A/C theory. Started misfiring today 30 minutes into driving, no A/C turned on. I'm still curious as to:

1. Chances of wiring harness failure and how to detect location of the failure in the harness.
2. Are there any relearning steps required after newly installed distributor and crank sensor?

Thanks.

Great point Joe, thanks. I'll make sure the shop addresses ECT sensor on 8/12. I'll let you know as soon as I learn. They typically are running a few days behind so it may be later rather than sooner.

Hey Joe, everything checked out okay except for crank sensor (CKS). Miss is occurring due to faulty CKS per their scanner. Based on their research (mine too after I got home today) they found where many off-brand sensors failed repeatedly (as in my case), but factory OEM sensor worked fine. Sound familiar?

I'm going to order part number 04807083 from Chrysler and see if that works. Will take a few days to get the part. The off-brand I was using was a BWD sensor p/n CSS48. Tried to find the max temperature for this part, but I cannot. Read where the sensor should be rated to at least 300 degrees.

Any info to add or dispute here is appreciated. Thanks. Ordering part tomorrow morning unless you can think of something else.

Latest:

Salvaged a $15.00 factory sensor from running motor at boneyard = same result. Ran great until operating temperature, then missed and jerked. Trying to not have to pop for a $100 sensor from factory, especially after exact same result from installing 5 different sensors. Following are questions related to air gap:

1. Does the flywheel (flex-plate) need to be in a certain position before installing new sensor in order to ensure proper gap?

2. Something is telling me that once the motor heats up, it expands and that expansion distorts the gap which affects sensor's performance (misfires).

3. I lightly glued (Elmer's paste stick).030 paper onto end to create the gap. Is there a better way to create this gap?

4. Trans-axle was removed to do freeze plug R&R by repair shop as mentioned in original post. Might they have adversely affected the flex-plate (reading windows) during this repair? Note shop in their latest scan on 8/12 said the flex-plate and reading windows were all intact and no issues. There is no clicking noise indicating issues in this area.

Also, in reply to your latest response, shop said all wires and connections were secure per their scan on 8/12.

Thanks.

Thanks, there's another shop in town that I can have scan. They're a couple of weeks out so it may be early Sept. Not sure how likely they are going to provide fuel feed and ECT data, but I can ask. I also might pop for a new factory sensor.

Really appreciate you hanging with me on this issue. Car is so pleasant to drive when running at specs. All new suspension and tires, tight and smooth with 200,000. Owned for 20 years, can't give it up.

Latest, note this is with the used OEM CKS sensor installed last week:

I drove yesterday morning for 20 minutes, no misses, no check engine light, parked it for 40 minutes. Now normally, it would begin to miss right at startup at this point (once it had been driven and then sat for a spell). No misses at startup and it ran great for another 20 minutes until I putted up to my garage, then it began to miss and check engine illuminated.

Today, I fired it up, check engine cleared itself (no light) for the first time during this mess, drove for 20 minutes, no problems, parked it, sat for 20 minutes, at restart it began to miss immediately and get this for a correlation, the A/C quit blowing cold air. Then 2 minutes later the miss cleared itself (while I was driving 40 mph), and the A/C began blowing cold air again. Once I got it home it started to miss again, but I couldn't tell if cold air stopped blowing. The check engine light never illuminated today.

Does the A/C correlation above help you in any way (diagnostically speaking)? Still planning on getting it re-scanned to get readings you requested. Probably be late next week.

Greetings Joe, can't believe it's almost been a month already since our last message. Had another shop scope my problem, but they did not share fuel or ECT reads. However they did provide insightful info which relates to your last post on 8/18.

1. Concluded that it's either the sensor wiring or damaged reluctor wheel. I'm hoping for the former. My question to you today (well there's actually a couple, few in this reply) is if the reluctor wheel is damaged (and this could have occurred when they removed and replaced the trans-axle to fix freeze plugs), but if the RW is damaged, would I be having intermittent issues? I'm thinking if the RW is damaged it would be a consistent miss all the way from start-up through warm-up. If it ends of being the RW, is this something that can be removed and replaced? This latest shop said they wouldn't try it due to the sensitivity of removed and replacing that particular part.

2. I remember back when I first thought the no start was CKP related, and I removed and replaced the sensor, I had trouble freeing the plug where it was attached to the frame with those plastic threaded grommet studs (mounted to the sensor plug in this case). Fought it pretty hard and twisted and such to finally get it free. This is when I could have damaged the plug end that runs down from the main harness. At any rate, latest shop suggested I hard wire the CKP sensor (eliminate the plug). Do you recommend doing this, or should I re-pin that side of the plug? If I hard wire, how do I know which wire goes where between the two ends of the plug? Is there a chance of crossing wires?

I'm hoping once I get it missing again, at idle especially, I can reach down an manipulate the plug (squeeze, twist) to remedy the miss. Oh how sweet that would be to just be the plug!

3. One last consideration is the cam sensor in the new distributor. This latest shop was getting CMP sensor faulty readings, but they said they were ghost readings related to the faulty CKP signal. They said it most likely isn't the CMP sensor, but I may removed and replace since it's under warranty and much easier to do than the RW.

Thanks Joe, hope all out in CA is well.

Thanks Joe, I'll let you know what I learn after cut and splice if that's what I elect to do.