Clicking (arcing?) on ignition rail. What to do next? - JeepForum.com
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post #1 of 31 Old 06-03-2020, 07:13 PM Thread Starter
WMWHV
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Clicking (arcing?) on ignition rail. What to do next?

My carefully maintained 2006 LJ Rubicon auto with 38K miles had been spending a bit too much time in the garage, but was running perfectly when last driven a few weeks back. A couple of years back, I went through the Hell of the camshaft position sensor/OPDA issue, but after getting a second new OPDA and sensor, that issue seems to be behind me. This is something different. I needed to get it inspected, so brought it out and noticed an intermittent rough idle and it would die while idling. Simply stop running. Was showing not ready for EVAP, Oxygen, Oxygen Heater and Catalyst. Thought that maybe I had disconnected the battery and not driven it enough to reset everything, so I started driving over the weekend. On occasion as I was driving, it would simply stop running. On the freeway. Occasional missing as well. Over a day or so of driving, the not readies cleared up except for the oxygen heater, but I know that is another story and it needs some wires snipped, etc. However, it was still missing occasionally and dying. At one point, I got a pending code for a misfire in cylinder 6, but it went away and never came back.

Then the Evap not ready code came back. Went through the drive cycle to reset it and it kept dying on occasion. When I checked the codes again, I was back to the same four not readies. I checked the resistance and voltages on the PCM connector pins as recommended in other threads and all was OK. Pin 11 was losing a tenth of a volt, but the resistance was about an ohm. Thought it could be a loose wire somewhere, so I ran the engine and shook connections and harnesses to see if I could isolate a problem. While I was under there, I started to hear a clicking sound that happened whenever the engine would miss. I eventually traced the sound to the back part of the ignition rail. I could not see a spark but figured there was arcing under it. I took it off and other than a little dust that reminded me of some fun off road trips (different colors for different places) nothing appeared out of the ordinary.

So, what do I do next? I think there was arcing under there, which was causing the clicking. Do I pull the plugs and replace them while I have the rail off? Do I replace the rail? Is there a way to test it? Am I barking up the wrong tree chasing the clicking noise? I would appreciate any suggestions as to next steps. Searched this forum, but maybe my search terms were bad, as I could not find an answer.

Thanks in advance.

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post #2 of 31 Old 06-03-2020, 07:45 PM
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The frequent monitor resets and idle problems sound like a low battery or battery connectivity issue, possibly due in part to the Jeep not being driven much. Add in the humid Houston environment and the resulting possibility for corrosion, I'd start with a good cleaning and tightening of all battery cable connections with special attention paid to ground G105 at the right rear of the engine block.

As for the clicking from the coil rail, anything that provides a conductive path can cause arcing from the connections between the rail and the plugs (inside the plug boots, they look like a spring), so I would clean the rail and inspect both it and the plug boots for cracking and holes. If the plugs are the original ones it couldn't hurt to swap them out if you wish, it would be a good idea to at least pull them to inspect/clean/regap as needed, and be sure to smear a little dielectric grease inside the plug boots when you reinstall everything.

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post #3 of 31 Old 06-03-2020, 07:57 PM Thread Starter
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It lives on a battery maintainer since it is not a daily driver. I think the battery (Optima Yellow Top) is OK. Was reading 12.6v if I recall correctly. I will take the ground connector off and clean it up just to be safe. It looks showroom from the outside.
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post #4 of 31 Old 06-03-2020, 08:42 PM
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Run it at night in a dark area and turn off the under hood light if equipped. You will be able to see any external arcing.

If they are the original plugs, they are due for a change. They are supposed to be changed every 30K unless they have been changed to dual platinums or iridiums.
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post #5 of 31 Old 06-03-2020, 09:22 PM
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Quote:
Originally Posted by jkp View Post
Run it at night in a dark area and turn off the under hood light if equipped. You will be able to see any external arcing.
Misting the running engine with a water spray bottle in the dark can really bring out any arcing that may be happening.

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post #6 of 31 Old 06-04-2020, 06:59 AM Thread Starter
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Pending any additional thoughts, sounds like my next steps are to replace the plugs with Autolite XP985s, clean up, but not replace the coil, reinstall with dielectric grease on the plug covers and clean up the ground connection, just in case. I will reassemble and do some night ops. Will ensure I use a bottle of water and not starter fluid to locate any arcing!
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post #7 of 31 Old 06-04-2020, 12:10 PM
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Since the misfire appears to be from #6 according to the code you get you are probably in the right area but consider it also might be arcing from the #6 injector wires. The injectors are fired by the PCM pulsing a ground to them. If that grounding wire is in contact with a 12v source you could get a spark each tine it gets that momentary ground signal. The injector harness runs across behind the engine & that is an area known to have the harness rub against a bolt & damage any of the various wires there. It is a tight space & hard to see back there but worth checking as well as the coil pack.


The #6 injector driver wire is brown/violet.
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post #8 of 31 Old 06-04-2020, 01:39 PM Thread Starter
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I have been trying to figure out how to see and better feel around back to better inspect those wires. I think the crankshaft position sensor wires are in there too. The harness appears to be clear of the engine, but the plastic loom has become "crunchy" over time in a few places. When I get my fingers inside the loom, the wires feel as if they remain separate and intact.
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post #9 of 31 Old 06-04-2020, 04:13 PM
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I think what happens is the harness drops down & there is a bolt that sticks through the firewall from the cab. There are enough wires in that harness that depending on what wire(s) get damaged any number of weird things can happen.

If damaged, I would think the harness would have to be laying on or very close to the bolt.
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post #10 of 31 Old 06-04-2020, 09:03 PM Thread Starter
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Well, another night, another challenge. The grounding stud came loose before the nut came off. I now know there is something called an external Torx socket, size 7, and that is what holds the end of the stud while you back off the nut. The spark plug replacement went easily. I buttoned everything up and no popping or missing, but the idle was perhaps a bit rough. All the not ready codes were gone except for the oxygen heater. I took it out for a drive. It seemed to run fine. I got off the freeway and as I was coming around the u-turn to head home, the check engine light started flashing. It was a misfire in cylinder 5. I cleared it and it came back. No clicking, no obvious missing. Yes, I put a plug in cylinder 5. Is the next step replacing the coil rail?
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post #11 of 31 Old 06-05-2020, 02:02 AM
rheology1
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My 2000 TJ started running rough and missing with a significant loss in power recently. It threw the misfire in cylinder 6 code. I changed the plugs and coil pack. Now itís running perfect again. Thereís a way to check your coil pack with a multimeter. You may wanna do that to rule it out.


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post #12 of 31 Old 06-05-2020, 01:31 PM
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The FSM lists a spec for the coil rail primary resistance which you can check with the rail in place. Disconnect the coil rail plug and measure from pin 2 (BR) to each other pin in the rail connector, you should see between 0.71 and 0.88 ohms for each one. Secondary resistance isn't listed, but typically will be in the 11kohm to 15kohm range when measured from pin 2 to the plug connector.

Information to keep in mind here is the coil rail contains three separate coils which each simultaneously fire two cylinders. The cylinders are paired to the coils such that their sum equals seven: one and six are paired, two and five are paired, and three and four are paired. From this we can discern that if a misfire is present on two paired cylinders then a specific coil or driver circuit may be suspect, whereas misfires on two unpaired cylinders makes this less likely. Also useful to know is the PCM uses the inductive kick sensed in the injector driver circuits and variation in rpm sensed in the crank sensor signal to identify a misfire and on which cylinder(s) it's occurring. Misfires can be caused by an ignition system fault, a fuel system fault be it electrical or fluid pressure/flow, or cylinder compression fault with the most likely problem here being poor valve sealing.

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post #13 of 31 Old 06-05-2020, 01:58 PM Thread Starter
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Quote:
Originally Posted by mukluk View Post
The FSM lists a spec for the coil rail primary resistance which you can check with the rail in place. Disconnect the coil rail plug and measure from pin 2 (BR) to each other pin in the rail connector, you should see between 0.71 and 0.88 ohms for each one. Secondary resistance isn't listed, but typically will be in the 11kohm to 15kohm range when measured from pin 2 to the plug connector.

Information to keep in mind here is the coil rail contains three separate coils which each simultaneously fire two cylinders. The cylinders are paired to the coils such that their sum equals seven: one and six are paired, two and five are paired, and three and four are paired. From this we can discern that if a misfire is present on two paired cylinders then a specific coil or driver circuit may be suspect, whereas misfires on two unpaired cylinders makes this less likely. Also useful to know is the PCM uses the inductive kick sensed in the injector driver circuits and variation in rpm sensed in the crank sensor signal to identify a misfire and on which cylinder(s) it's occurring. Misfires can be caused by an ignition system fault, a fuel system fault be it electrical or fluid pressure/flow, or cylinder compression fault with the most likely problem here being poor valve sealing.
This is most helpful information. I was preparing to start researching to figure out the basis for the misfire code, since there is no sensor on the coil. The fact that the problem last occurred as I was in the apex of a fairly tight u-turn and that I got a misfire earlier on 6 before now having a steady indicator on 5 makes me think I am dealing with a sensor/computer/wiring issue. I don't think I can get to the connector with the rail on the Jeep, but it is not that big of a deal to remove it. I probably will pull it off just to ensure that is not the source of the problem, but I suspect the problem lies elsewhere. I keep wondering about the crank sensor...
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post #14 of 31 Old 06-05-2020, 08:22 PM Thread Starter
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I appreciate you guys hanging in there with me. My brain is fried at this point and I am going to call it a night. Here is the update: I visually and/or manually checked all the wiring harnesses from the top and bottom. There were no issue where a bolt or anything else has penetrated the loom. All connectors appear intact. I pulled the crankshaft position sensor. The wiring and connector looked good. Cleaned them up and put on some Boeshield T-9. There were a few metal shavings on the sensor and I removed them. I went ahead and took off the throttle body and cleaned it and reassembled it. I measured the resistance on the number 5 injector. It was within normal limits. Connector and wiring looks great. Fired it up. Almost immediately got P0300 - multiple misfires while idling in the garage. The exhaust has a rhythmic put-put-put sound like it is missing. Also noticed a lot of water and soot coming out of the exhaust pipe. Started and stopped a few times and got the P0300 each time. Idle was rough. Cleared the codes and drove around the neighborhood. Got the flashing CEL. Ran rough, got home and the code was P0305 - misfire on cylinder 5 again, like last night. This happened a couple of times. I cleared the codes again and took a couple of loops around the neighborhood. Now, no codes at all and the incomplete emissions tests are starting to show OK. Just the Evap left to go, and that one needs to sit overnight to reset. Yet, it still idles rough. It also knocks just a bit on acceleration. Otherwise seems to be running OK. I did not want to put it on the freeway. I did not check the coil rail, but based on what is happening, it does not seem that could be the problem, but if I need to pull it off to check it, I can. I keep going back to this statement: "Misfires can be caused by an ignition system fault, a fuel system fault be it electrical or fluid pressure/flow, or cylinder compression fault with the most likely problem here being poor valve sealing." Since I dealt with the OPDA CPS issue a couple of years ago, I naturally gravitate toward thinking this is some sort of sensor issue. I recognize I need to step back and reanalyze this, but I am not sure where to start. Perhaps something will come to me in a dream tonight... Is there such a thing as a computer or scope that can give a real-time picture of what is going on with all the sensors, injectors, etc.? If I could see all that data and what was happening on all the systems when the problems occur, that would tell me a lot. My code reader gives me only limited real-time data and does not graph it. Any additional thoughts would be appreciated.
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post #15 of 31 Old 06-05-2020, 10:15 PM
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It couldn't hurt to still perform a resistance check of the coil rail primary and secondary circuits as having more data usually isn't a bad thing, might as well do the water mist on the running engine check as well just to rule out any arcing. Following the theme of more info is a good thing, maybe check to see that you're getting very close to battery voltage at pin 2 of the rail's plug when the ASD relay is energised. Speaking of which, I'd add checking the voltage present at #5 injector's plug brown wire when the ASD relay is energised, and if possible monitor the injector circuit's function with a noid light to see if there's an erratic flashing. A good method of testing whether a misfire is due to a faulty injector is to swap the suspect one with another on the engine that doesn't have any issues -- if the misfire follows the suspect injector, that pretty well verifies that it's bad.

Other thoughts that come to mind would be to try dumping a bottle of gas dryer in the tank or topping up with fresh fuel if it's been a while since your last fill up, maybe check your fuel pressure as well to make sure it's in spec (58psi +/-2). I realise you keep the battery hooked up to a tender, but if it's more than a few years old it may be worth having it load tested -- modern Jeeps can do all sorts of weird things when their battery is subpar. Getting into less common tools, performing a leak down test can tell us if you have a valve sealing problem. On a slight tangent, it's been my experience that these Jeeps don't like sitting undriven for extended periods and especially not just being driven for short trips -- sometimes all that's really needed is a good extended high speed drive to get things up to temp, and maybe a little spirited driving in there as well to help burn out the carbon.

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