Misfires and rough idle

[Searcher67]

2002 Libby:
NEW:
Heads, coil packs, plugs, cam and crank position sensors

Compression test OK
Leak down test OK

Runs fine when driving, 18MPG

at idle random misfires
spark advance swings from 0-17
idles a little rough

Test equipment: Mac Task master

OH, there are NO codes in ECM....

If I had hair, I'd be pulling it out now... Please help cause I I'd look funny without eyebrows.

 

[Searcher67]

OK, here's an update... I was researching here and I found someone that installed E3 plugs... He too had the random misfires.. SO, since I recently installed the E3s, they are coming out and I'm buying the ZFR6F-11G plugs. I will update after this task is complete!
Here's to hoping for the best!

 

[ridenby]

Yeah they seem to like copper plugs way better than the fancier ones.

 

[CzarKJ]

Copper all the way. Changed mine a week or two ago and it runs awesome. I used champion copper plugs.

 

[martin_metal_88]

Damn we should start to count how many time it end to using copper plug. The jeep like them so much and they are so cheap XD

 

[Searcher67]

WELP, Changed to the ZFR6F NGK, and am still getting misfires at random... Geeze this is really starting to stress me out..

 

[Snail Farmer]

When mine was doing that, it ended up being the O2 sensors. But I was getting a P0300 code also, so not sure if that'll do anything for yours.

 

[Searcher67]

Yeah, I thought the O2 sensors as well, but the sensors all are functioning normally.
My problems ONLY occur during start-up and when at idle. On the gas, all is great, on the freeway all is great. Power is normal, acceleration is great. I only have the issues when at idle.

 

[Searcher67]

OK, here is another thought on this issue. Everything was golden last week, no misfires to the point I even took away the OBDII computer.. (Kept it in the Jeep though) went for several full tank drives with no problems.. Then off to work, still nothing bad. Then leaving work I started the Jeep and it was really rough. Plugged in the Task master and saw multiple misfires in #6 and random misfires across both banks. Went through the hell of changing out the crankshaft position sensor and that's when I found oil in the plug, running down the harness. Ok, oil fouling the senor I thought. I traced the oil leak to the Cam shaft sensor.. Took it back to the shop where they swapped out the CPS under warranty, ( New heads installed). Still terrible random misfires, making no sense at all. All the coil packs and plugs are NEW. I swapped out a coil pack under its lifetime warranty through O'rileys auto because it gave the most misfires. Still random misfires across both banks. By now I am at wits end with nowhere to turn anymore.
So bad it's keeping me awake.. Then it hit me, what happened between running golden to crappy? A TANK OF GAS! I filled up that night before going to work. I have a short commute so I am assuming I barely got into the new fuel by the time I got to work that day. By the time I left I was into the new fuel and thereby comes the misfires..

This morning, I ran up to O'rileys to pick up a new ASD, (none in stock) and a can of seafoam, then put in a half tank of super from Chevron.. After the drive home and ten minutes of idling I have not had a single misfire!

So, BAD GAS?

Will keep updating as things progress...

 

[dude1116]

WELP, Changed to the ZFR6F NGK, and am still getting misfires at random... Geeze this is really starting to stress me out..

Aren't those nickel, not copper?

OK, here is another thought on this issue. Everything was golden last week, no misfires to the point I even took away the OBDII computer.. (Kept it in the Jeep though) went for several full tank drives with no problems.. Then off to work, still nothing bad. Then leaving work I started the Jeep and it was really rough. Plugged in the Task master and saw multiple misfires in #6 and random misfires across both banks. Went through the hell of changing out the crankshaft position sensor and that's when I found oil in the plug, running down the harness. Ok, oil fouling the senor I thought. I traced the oil leak to the Cam shaft sensor.. Took it back to the shop where they swapped out the CPS under warranty, ( New heads installed). Still terrible random misfires, making no sense at all. All the coil packs and plugs are NEW. I swapped out a coil pack under its lifetime warranty through O'rileys auto because it gave the most misfires. Still random misfires across both banks. By now I am at wits end with nowhere to turn anymore.
So bad it's keeping me awake.. Then it hit me, what happened between running golden to crappy? A TANK OF GAS! I filled up that night before going to work. I have a short commute so I am assuming I barely got into the new fuel by the time I got to work that day. By the time I left I was into the new fuel and thereby comes the misfires..

This morning, I ran up to O'rileys to pick up a new ASD, (none in stock) and a can of seafoam, then put in a half tank of super from Chevron.. After the drive home and ten minutes of idling I have not had a single misfire!

So, BAD GAS?

Will keep updating as things progress...

Very interesting! I hope it's solved for you!

 

[Searcher67]

Those plugs are the recommended plugs for the Jeep as per emissions decal on the core support. Which is why I went with that.. Heading out for a long drive.. Will know more later

 

[doolop]

Check the wires going to the coils and fuel injectors. This was my gremlin.

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[Searcher67]

Sorry for the late reply, been away.. Had the Jeep out in the Mts for 4 days.. Running great although I can still feel an occasional misfire. I took the damn computer away from sight, simply got tire of looking at it and since there are no codes I figure let it be. I'll just wait for a code to be thrown then worry about it again.

While heading up the trail I did however loose a spring in the RR drum. Got this horrible squealing that stopped when I hit the brakes.. Pulled over, felt the wheel and it was HOT! So, I took it off, pulled the drum on the trail and out fell spring parts.. OH Well, slapped it back together and continued on my trip..
Did wonderful hardly felt the lack of one brake..

I did replace the rear brakes and hardware once we got home.

But, all is well and the misfire mystery continues...

On that note, Where we camped there was another newer Libby.. I heard it start early one morning and boy was that thing misfiring terrible.. I so wanted to stop him and plug in the computer to see what was going on with it.!

 

[Packdog]

Clean the IAC?

Have you tried cleaning the IAC? Those can cause rough idle with random misfires without throwing any codes.

This is a good thread on cleaning them:

http://www.jeepkj.com/forum/f196/vibrations-rough-idle-46693/