Rocky Mountain Billy Goat Build

It’s my understanding that fuel pumps rarely, if ever, go bad in stages - it seems to be all or nothing. I’m wondering if maybe it’s the cats, most my trips are short and around town. Only 60,000 on it but since there was a small timing issue before that could have plugged them up.
 
Alright, I pulled off the throttle body just to give it a good clean. Nothing there was alarming, but it’s nice to know it’s clean.

Letting it just sit running in the garage around 2,000 RPM and eventually the p0335 pops up again after a few stalls and a bunch of not wanting to catch. I’ve traced all the wires a dozen times, but I guess since that seems to be consistently involved in this headache I’ll order another MOPAR sensor and see.

In the mean time, I’m going to pull the cat section off the exhaust and see if there’s anything worth noting there. I need to do some work to it anyway.
 
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Well this was a pleasant surprise, and I probably should have done this during the tummy tuck. After loosening the cat to muffler linkage my exhaust settled a bit. I tightened it back up and all the previous interference I was expecting with the engine skid (and a slight touch of the upper control arm frame mount) cleared up.

It also dropped the pipe down a bit away from the CKS - part of me is wondering if excessive heat has just caused that part to fail. It won’t be here until after a short family trip - so I won’t know for a bit.

Armored up!

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New crank position sensor installed and no signs after about 50 miles. More time will be useful. I also loomed the wires again and wrapped the nearby exhaust - hoping maybe it was just heat that triggered the issue. If this one “goes bad” again, I’ll have to deep dive into tracing wires.
 
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Today a few stumbles, surges and stalls. The only code, that cleared itself, is p0300 (random misfire). This has only been when stopped or approaching a stop, which suggests to me it’s something new in the idle system (or at least more pronounced there).

I think the candidates are IAC, Coil Rail Intake Manifold gasket and Spark plugs.

Ruling down the list:

1. possible, it was just off for a clean with the throttle body, maybe I messed it up.

2. also possible

3. Unlikely The plugs are new from last fall, the auto lite iridium set, so that’s unlikely since I’ve also checked them a month ago.

4. My exhaust did move a bit in my tummy tuck and subsequently when I loosened the muffler connection. I’m wondering if I did some damage to it. is the only way to know taking it apart?
 
tworley said:
Can you shake the wiring harness while it is running to see if it will stumble at all? Maybe there is a short somewhere in the insulation. Just a thought....

Also, have you seen this TSB? Sounds similar to what you are experiencing
https://wranglertjforum.com/attachments/tsb_wj_1803103-pdf.38661/
Click to expand...

Ive been trying to shake all the wires I can, so far I’ve not found anything. That’s the heat soak TSB I think? I don’t think that causes this, but I’ll try pretty much anything...
 
rasband said:
Ive been trying to shake all the wires I can, so far I’ve not found anything. That’s the heat soak TSB I think? I don’t think that causes this, but I’ll try pretty much anything...
Click to expand...

The fact the TSB refers to the cylinder 3 misfire and your reference to rail is what makes me think they could be connected. Speculation though as your engine is obviously different compared to my early 4.0
 
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It is hard to track intermittent issues. Looking at your past posts, you checked the cam sensor and crank sensor. I would check ALL of your grounds. Clean, tighten, make sure they are secure. There are several that go to body, chassis, etc. Reference the wiring diagram in service manual, it has diagrams of all the grounds.

I have worked in the construction/industrial electrical industry for 20 years, and seems so many issues are caused/resolved because of missing/loose, neutral/ground connections.
 
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motomick76 said:
It is hard to track intermittent issues. Looking at your past posts, you checked the cam sensor and crank sensor. I would check ALL of your grounds. Clean, tighten, make sure they are secure. There are several that go to body, chassis, etc. Reference the wiring diagram in service manual, it has diagrams of all the grounds.

I have worked in the construction/industrial electrical industry for 20 years, and seems so many issues are caused/resolved because of missing/loose, neutral/ground connections.
Click to expand...

I’ll go through these, definitely worth a pass. The one I remember not being able to loosen is the stud on the passenger side of the block (this was back when I was updating the battery cables). However I’m sure there’s more grounds I haven’t checked.
 
rasband said:
I’ll go through these, definitely worth a pass. The one I remember not being able to loosen is the stud on the passenger side of the block (this was back when I was updating the battery cables). However I’m sure there’s more grounds I haven’t checked.
Click to expand...

If you can not find anything significant, I would check the PCM connections, the wire harness connection at center of firewall, and anything between the crank sensor/cam position. Make sure they are dry, no rust or contaminates.

How about the plugs? Have you looked at those? If one is slightly different coloring, it could be indicator of which cylinder/s having an issue.
 
motomick76 said:
If you can not find anything significant, I would check the PCM connections, the wire harness connection at center of firewall, and anything between the crank sensor/cam position. Make sure they are dry, no rust or contaminates.

How about the plugs? Have you looked at those? If one is slightly different coloring, it could be indicator of which cylinder/s having an issue.
Click to expand...

The block ground was pretty well seized - I had a new battery cable sitting there and had to cut the bundle free, then I could get the stud out. I got a new terminal, crimped the bundle in, and installed the new battery cable. I grabbed a new 5/16ths bolt to make sure the contact for grounding is good. The rest of the grounds I went through in the fall but did an overview and they seem ok - I even scuffed up the metal more.

Could you expand on "anything between the crank sensor/cam position" - do you mean to pull the sensors and make sure they aren't fouled up or damaged?

The plugs I did in the fall and pulled them a month or so ago, but I didn't compare them side-by-side to see if they are wearing evenly - that's a good idea thanks!

045947A2-6DE9-4767-9F64-A92B6A7173ED.jpeg


Update: no changes, however it only seems to be at idle. If I leave my hand throttle revved a little it seems fine. Going to try the IAC since the risk is low in changing that.
 
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Sometimes looking at the plugs can give you a clue as to what is happening, such one may be blacker, and rest brownish color; or one is maybe wet, which would indicate ignition issue. Those are fresh, so we could rule that out.

I meant just check any connection between the cam and crank sensor back to PCM.

If your issue is only at idle, and goes once RPM are up, maybe try an IAC.

How does it act under load, such as driving along, engine at low rpm, and go full throttle? Does it stumble, or does it accelerate without a miss? Sometimes engines act different when under a load and just parked running with no load.
 
motomick76 said:
If your issue is only at idle, and goes once RPM are up, maybe try an IAC.

How does it act under load, such as driving along, engine at low rpm, and go full throttle? Does it stumble, or does it accelerate without a miss? Sometimes engines act different when under a load and just parked running with no load.
Click to expand...

I thought it was only idle and have an IAC inbound, however then driving around today it went into limp mode under power - so there goes that hope. P0300 (random misfire, that I never feel) and P0344 (cam position sensor).

I can’t feel any studders or misses - I think I may need to start removing the looms and tracing everything. I forget which post; but also stumbled on this test for the PCM power and ground chttps://wranglertjforum.com/attachments/checking-the-pcm-and-ground-circuits-pdf.173914/

Here’s the plugs I pulled this morning, these are in order from back (left) to front (right) - only a very minor discoloration on the first one on the left. I tested the coil with a multimeter too, it is in spec.

BF06B139-D3C5-4EAC-8C3A-789E0F24F133.jpeg


My battery is from 2016, but measured well. Perhaps I need to do a load test on it too.
 
I do not think your battery would cause this issue. If it starts the motor, it should be fine. Your plugs are not showing anything significant either. I am running out of ideas for you, but I would definitely follow the tread, see if you can find anything.
 
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One other thing to check before you start pulling loom and tracing wires (which is a great idea) is to check your connections at the PCM. I was experiencing intermittent issues and my crank sensor was loosing voltage intermittently. Long story short--the connections at the PCM had become slightly unseated (no idea how). I went thru a couple crank and cam sensors before I checked this. The connections "clicked" into place and I havent seen the problem pop up sense. This was almost 50k miles ago.
 
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tworley said:
One other thing to check before you start pulling loom and tracing wires (which is a great idea) is to check your connections at the PCM. I was experiencing intermittent issues and my crank sensor was loosing voltage intermittently. Long story short--the connections at the PCM had become slightly unseated (no idea how). I went thru a couple crank and cam sensors before I checked this. The connections "clicked" into place and I havent seen the problem pop up sense. This was almost 50k miles ago.
Click to expand...


A lot of our stuff on TJ's is approaching 15-20 years old, and expect them to work like they are only 5 years old. With age and other variables, connections do not connect like they did when new. We may see problems that cannot be clearly defined in a service manual or replacing parts.
 
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tworley said:
One other thing to check before you start pulling loom and tracing wires (which is a great idea) is to check your connections at the PCM. I was experiencing intermittent issues and my crank sensor was loosing voltage intermittently. Long story short--the connections at the PCM had become slightly unseated (no idea how). I went thru a couple crank and cam sensors before I checked this. The connections "clicked" into place and I havent seen the problem pop up sense. This was almost 50k miles ago.
Click to expand...

Good idea, I will go through this again. I used a toothpick this morning to get some dielectric grease in each little pin - but should probably focus on if any of the pins are off and to make sure they seat right. I've shaken these a bit without any noticeable impacts on the engine, but we all know some times conditions aren't always right to reproduce issues.

It's feeling like I am quickly approaching the loom, timing, or PCM being the last few remaining things.

I've been thinking about buying a truck for a bit... maybe I just use that money to do an engine swap (this is the nuclear option :D )
 
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