Either a coil or plug any ideas?

[Soldier777]

So I have a real rough idle and it jerks while driving, not all the time its very random. Whats the best way to tell which one is it and where it is?

 

[toms89]

I don't know of any way to tell which plug it is other than if the computer sets a code letting you know which cylinder has a misfire. Chances are if you pull all the plugs you may find it. Water in plug hole, carbon tracking, or fouled plug. Being intermittent in nature makes it more difficult to locate.

 

[Soldier777]

I know I was just hoping there was an easy way lol... i will just have to start taking them out 1 by 1.

 

[toms89]

Well I have heard you can find a weak or dead cylinder by checking exhaust temps at the primaries of headers.(it would be cooler than the others). Not sure this would work all that well with the stock cast iron manifold.

I suppose you could pull plug on coil one at a time until you find the one with the least change in rpm/idle. This would likely set code on computer though.

 

[Soldier777]

Thanks for the Ideas. I am just annoyed because I am not throwing any codes and it is soooooo random... I would be much happier if it just said #2 haha.. I guess the expy just wants to spend some extra time with me

 

[alaskanexpy]

had this issue with my excursion. new set of ebay coils and new plugs...bam runs like new!

 

[Soldier777]

had this issue with my excursion. new set of ebay coils and new plugs...bam runs like new!

Did you do all of them or just the bad one?

 

[alaskanexpy]

since the ebay ones were decently cheap($120 for 10) i did all of them.

 

[walnuts4x4]

yeah I had same problem last year... took weeks to get the CEL to come on... so a set of 8 cops from global automotive for less than 100 shipped and some autolite double platinum from autozone with military discount and bam... good to go

 

[Expeditionary]

i have the same misfire, my mechanic said, "well you may have a bad plug, or it could be a coil, then again it could be plug wires, you may also need a MAF, it could also be an O2 sensor, or something else".... I left it and drive it that way as it only misses sometimes

 

[Thermo]

Soldier, I would first recommend doing a visual inspection of the top of each of your COPs. If you look at them, you will see a clear top to them. If you see a white line in any of them (the white line means there is a crack in the epoxy top), you are getting a little bit of water inside the coil and it is affecting the amount of spark, leading to the misfire. I would first check 3 COPs though as they are the most likely suspects (in order of most likely to fail): #4, #3, #7. The two on the passenger side are tucked in a low air flow area and they tend to get really hot, which will lead to their failure. #7 (driver's side) is right under the EGR piping. ANother one that sees a lot of heat.

After that, odds are you are looking at having to pull each COP and seeing if the rubber boot is in good condition and not shorting through the boot to the wall of the plug tube. I have heard that roughly have of the "bad COPs" were attributed to bad rubber boots. If you talk with your local auto parts store, you can buy just the boots.

 

[Soldier777]

thanks everyone i am diving in to this on friday night. I am replacing my calipers and pads so I might as well solve this annoying little problem as well. I will let you know what I find out

 

[Soldier777]

ok update.. I finally threw a code and it came up o2 sensor bank 1 sensor 2. I will be trying to fix this soon, I just would of never thought it would be that. I truly believed it was a plug. Just out of curiosity could my strait pipes be the culprit of this? Can i just disconnect the battery to see if it will "reset"?

Thermo I did look over all the coils and none of them had what you described.

 

[Tigster]

www.rockauto.com has some pretty good prices too if you decide to do cop and plugs. They also sell the boots.