Engine sputters when turning on high beams

[Ryanoceros]

I got the PCM back today. The WranglerFix guys couldn't recreate the issues though I appreciate you fellas for the help!

With that ruled out I tested my ignition switch, plug, and harness today and it's also fine. I swapped the crank sensor years ago with no change. I'm going to check the opda and cam sensor tomorrow. Back in 2020 I switched to the crown unit and kept the Mopar sensor and I'm wondering if it's on its way out finally. I have the crown cps I could try but idk if my cam and crank are in tight enough relation for it to work without throwing a code and I don't have a thinkdiag or DBR to adjust it. I assume if I throw it in with the vehicle already up to op temp that I can tell if the issue is still present or not before it throws a code.

I'll report back.

 

[Ryanoceros]

Checked the OPDA today and CPS. It's a crown replacement and it didn't feel or sound great. Wouldn't spin if I gave it a quick twist and had a little squeak to it when spinning it slowly. It's only 5 years old with about 18k miles on it. I threw the old mopar one back in (which was fine when I preventatively replaced it) and tried the crown sensor that I never used and the problem is the same so I'm gonna rule out the cam sensor for now as well. It idles fine most the time, occasional sputter, until I punch the gas and it'll spit and sputter until it kills the engine as long as I hold the throttle. I'm gonna tear into the throttle body, tps, iac and fuel pump stuff next I think.

Also check your OPDAs, even if you've replaced them already.

 

[Ryanoceros]

TPS and plug tested good. Swapped it with one I had on hand anyways and it didn't change anything. Throttle body, IAC and MAP are all clean and working good, I assume anyways. Unplugging the iac kills the engine and unplugging the maf makes the idle surge so still possible suspects but it seems like they're doing what they're supposed to be. I'm not sure how else to test those.

This is the craziest issue I've seen in a while haha. Challenging to say the least.

 

[k1n3k]

I'm going to toss my 2 cents in. From what your vid shows, looks like there is high resistance/bad connection somewhere. My thought is that when you flick on your high beams, there is an instantaneous draw much higher than the normal amp draw of the bulbs while the filaments are cold. This is high enough current to drop the voltage low enough the ECU has a fit. I'm not an expert on the electrical systems in the TJ, but I believe the only place the two circuits share a common positive leg is in the power distribution block. I'd check the voltage drop between the battery positive post and the input of the distribution block. Check it with the engine OFF with the lights ON. You'll just put one lead of your MM on the battery positive (directly on the battery post itself, not the cable clamp), and the other on the distribution block input (the sheet metal piece of the block, not the lug or wire) and see what voltage is there. If you see much more than ~.6v-.8v difference between those two spots, I'd be thinking the main power feed to the distro block is suspect.

The other thing to check is the grounds in the vehicle. Again, not an expert on the electrical system but I believe the main ground cable is split at the battery post, one lead going to the body somewhere, and the other going to the engine block. If the ground going to the body has a bad connection, that could cause the same issue you're seeing as well. I'm not sure what grounding exists between the body and the engine outside of the dedicated branch from the battery, but I would check the voltage drop between the body and the negative battery post. I'd expect very little voltage there as well with the headlights on, again I'd expect ~.6v or less.

If you'll measure those things and report back what you find, I'll see if I can come up with other theories or other tests to run.

Quick edit: I see you have the toyota wiring harness installed for the headlights. Where did you wire in your power feed and your ground?

 

[Ryanoceros]

I'm going to toss my 2 cents in. From what your vid shows, looks like there is high resistance/bad connection somewhere. My thought is that when you flick on your high beams, there is an instantaneous draw much higher than the normal amp draw of the bulbs while the filaments are cold. This is high enough current to drop the voltage low enough the ECU has a fit. I'm not an expert on the electrical systems in the TJ, but I believe the only place the two circuits share a common positive leg is in the power distribution block. I'd check the voltage drop between the battery positive post and the input of the distribution block. Check it with the engine OFF with the lights ON. You'll just put one lead of your MM on the battery positive (directly on the battery post itself, not the cable clamp), and the other on the distribution block input (the sheet metal piece of the block, not the lug or wire) and see what voltage is there. If you see much more than ~.6v-.8v difference between those two spots, I'd be thinking the main power feed to the distro block is suspect.

The other thing to check is the grounds in the vehicle. Again, not an expert on the electrical system but I believe the main ground cable is split at the battery post, one lead going to the body somewhere, and the other going to the engine block. If the ground going to the body has a bad connection, that could cause the same issue you're seeing as well. I'm not sure what grounding exists between the body and the engine outside of the dedicated branch from the battery, but I would check the voltage drop between the body and the negative battery post. I'd expect very little voltage there as well with the headlights on, again I'd expect ~.6v or less.

If you'll measure those things and report back what you find, I'll see if I can come up with other theories or other tests to run.

Quick edit: I see you have the toyota wiring harness installed for the headlights. Where did you wire in your power feed and your ground?

The power for the headlights comes straight from the battery and I think ground is to a stud near the front grille somewhere but I'll confirm later, it's been a few years. I do have the big 7 mod as well, replacing the battery, pdc, alternator cable, and grounds with new heavy wire. I'll go through and follow that path as well just to rule out any potential issues.

I'm thinking possibly a combo of battery and alternator at the moment. A couple guys have mentioned it in the thread already and I'm gonna dig deeper on that. My alternator tops out at like 13.5V and I've been through a few batteries since I bought this thing back in 2017. I know TJs are sensitive to voltage but maybe moreso than I thought. I had a code for the TPS yesterday while I was testing all my sensors. My battery was at like 11.8V from all the starting and stopping but when I hooked a jump pack to it the code went away. I've got batteries but unfortunately the only way to test that theory is to buy a new alternator, which I may have to bite the bullet and do. Wild if it's something so simple but things are pointing that way.

Thanks for all the help! I'll report back.

 

[k1n3k]

Ok, knowing you have the Toyota harness attached directly to the battery does change things. The high power bulbs are also going to be really power hungry while the filaments are cold. I'm thinking you're looking at a weak battery. The alternator may be failing with a bad diode, that would damage batteries while still charging. You can check to see if you have a bad diode by testing for AC ripple across the battery, just set your meter to AC and see if you get some voltage. Remember the alternators job is to charge the battery, not accommodate instantaneous load changes. The battery should have enough beans to take the load of the lights being switched on without it drawing down too far. Have your battery tested with a REAL tester. The type that has a large bank of resistors and actually puts a good load on it, not the garbage electronic testers. Before you replace the alternator, have it tested as well. replacements are so bad nowadays that it might be a step backwards to replace it.

 

[OilSpot74]

Breathing some life into this post. The issue has finally gotten worse. Rather than being intermittent it's happening every time I run the vehicle and it's completely undriveable. The alternator did seems to test fine a couple years back when I was messing with it still.

Things that stand out:

- Only happens at operating temp
- I've done the big 7 mod
- Pressing the throttle makes the engine sputter and cel flash like turning the high beams on does
- Sometimes it'll sit and sputter on it's own with no input from me, to the point it'll kill the engine
- No codes stored

I'll attach a video. At this point I'm thinking coil rail or pcm. Honorable mention to the ignition switch but I have doubts.
https://photos.app.goo.gl/R2WJ5Psp7HHHNvsf6

I appreciate you fellas!

Normally flashing CEL is a computer issue. (If it’s constantly on and flashing that is)

 

[Ryanoceros]

Normally flashing CEL is a computer issue. (If it’s constantly on and flashing that is)

Yea I'm still leaning that way myself. It's not constantly on and flashing, just flashes in rhythm with the misfires. Wranglerfix couldn't replicate the issue with my PCM but it's the only thing that remains other than the coil at this point.

Replaced the alternator today with no change. Redid the bundle of grounds on the passenger side of the block beside the opda with no change. Went through TPS, IAC, and CPS pigtails looking for damage and checking for 5v. Unraveled about a foot of wire loom from each plug from the PCM to check for damage. Inspected the PDC terminals, especially in the ASD relay block.

Been staring at this thing, that I just lifted and put on 35s after 8 years of waiting, since September because I can't drive it haha. Haven't even broken in the gears yet. Brought to it's knees by an electrical issue. I'm gonna sit here for a bit with a wranglerfix PCM in my cart. I'll update after I buy it and try or or decide in something else.

 

[k1n3k]

Just a dumb idea, but get the thing back up to operating temp, then take your garden hose or a water bottle or whatever and spray the crank position sensor. If it runs normal again, replace it. I saw you messed with the OPDA and the cam position sensor, you ever mess with the crank sensor?