Ok for a liitle while now every now and then my 02 navigator would start randomly mis-firing would last less than a minute then stop check engine light would flash while it was happening. When I checked the codes it said mis-fire in cylinder 8 detected. Well yesterday I went on about a 40 mile trip it ran fine the whole time i got home went in for about 3 hours came back out to leave but when i started it up it was running horribly really rough, sputtering and almost stalling, back firing all at idle. When i would rev it up past like 1300-1500 it seemed to smooth out but when i let off to let it idle it would run horrible again. when i shut it off and restarted it, it almost didnt want to start but whne it did it was still them same. So I hooked the code reader back up and now its saying mis-fire cylinder 6 detected, mis-fire cylinder 8 pending, mis-fire cyclinder 1 pending. now i have read about the problem with the head when you get multiple mis fire codes but from what i have read its only on the drivers side and i dont think it is the head now seeing as it says cylinder 1 now also. Please any help would be appreciated.

 

If it has the original COPs in it, then they could be on their last leg making it time to start replacing them. Are the spark plug original or have they been changed?

 

honestly i couldn't tell you i picked the vehicle up about 3k miles ago. the person that owned it before me said they replaced one of the cop's because it was mis firing im am not sure which one though. has anyone had any issues like this?

 

also the cop's everyone buys off ebay do they come with springs and boots?

 

From what I saw when searching ebay for COP or DG-508 they all come with springs & boots.
Actually your coils may not be bad, they can be tested with a VOM.
Your spring & boots may be all that is bad.
The misfire may not be that the coil is not firing.
It is more likely the spring is rusty or the boot has degraded and the path of least resistance for the current is to the head.
I think it is easier (more profit) for vendors to sell the entire assembly.
It seems odd that several cylinders on opposite sides of the engine are all going bad at the same time.
Did you check the vacuum line to the PCV valve?

 

no i have not checked the vacuum line? what would i be checking it for?

 

You have a pcv rubber tee on the passenger side of the engine that fails/leaks after time. This vacuum leak will give you a poor running engine and prompt for misfire codes.
R&T is right on. Check your boots and springs. When changing your plugs if not already done, use a liberal amount of dielectric grease on the boot connections and anti-sieze on the plug threads. More than likely, these items will fix the problem.

 

ok ill try those things first. I have also been told that a common problem when changing the spark plugs is the threads coming out when removing the plugs and that they are easy to strip when putting them back in. Has anyone had any problems like this? Another thing I forgot to mention was before it was running this bad about a week ago when we had a really bad rain storm and it had seemed to be mis-firing allot more that day. Also it had originally started with cylinder 6 i cleared that code then it came back a few days later as cylinder 8 that went away on its own after about a week and now its where it is now cylinders 1, 6, and 8.

 

Yes. You have to very careful as this has been a problem. Even more so with the newer years, the 2 piece plug breaks and leaves you with part of the plug still in the cylinder. Vacuum out the hole and spray one of the thread penetrators type products overnight prior to removing the plugs. Always use a piece of small rubber hose to re-thread the new plugs to ensure you don't cross thread.
I've seen moisture build up in the plug holes deep enough to cause a misfire. If you have a very humid day or rain, this could affect these misfires.

 

Ok here's some more info. I started it up and listened to it again this time with the hood up and I stood in front of it. Well the popping that I heard which I thought was the exhaust back firing the noise is actually coming from directly under the drivers side valve cover a litte past mid engine toward the back. My father came over and listened to it he's really good with cars and has always fixed his own cars since he was a kid he said it almost sounds like a burnt valve.

 

Its hard for me to hear that noise from here , but what you might just be hearing is the spark shorting to ground (or worse, the plug has come loose.)

Assuming you have the 5.4L 32-valve engine, is there anything that would prevent you from removing the driver's side ignition coil cover plate so you could check for high voltage spark leaking to ground or a spark plug that has come loose/out?

 

you might have a intake leak,water gets in your plug holes and causes mis fire.early morn. drives will be ok as the motor gets hot it drips water in spark plug holes.i've ran into this more than once.

 

yes i can take the cover off. it doesnt sound like its grounding out it does almost sound like the plug might have come out. also before it would get better when i reved it but now it stays the same. i am gona try to work on it later today since i finally have some free time assuming the temp stays under 100 today hopefully.

 

Ok I did some investigating and the popping sound was in fact a spark plug that had come out of the block. Now the bad news the inside of the end of the spark plug all the way up to the hex nut is gone. it must have blown apart inside the cylinder. oh and the threads from the block are still attached to the spark plug. I looked down inside with a flashlight and the top of the piston was covered in a caked on layer of what looked like oil covered dirt/debris/ and possibly spark plug pieces. This is cylinder 6 i think. the second one in on drivers side. i also pulled the other 2 COP's i could reach off and all of the springs in them looked clean and almost new looking. Now this i think is far to big of a job for me to tackle so i was wondering if anyone had any ideas on how much it should cost to have the threads replaced, cylinder cleaned out (assuming cylinder and piston are not damaged), all spark plugs and COP's replaced (i would supply COP's). Thanks everyone for all your insight and help with my situation.

 

If you asked a Dealer to do all that I bet the bill will be thousands.
If it's only the one sparkplug, and #6 is easy to get at, you might try repairing this yourself.
I am not an expert and have never tried this but those thread inserts are available w/instructions.
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I'd repair one item at a time and see how things improve before attempting the next.
Your COP's may not be bad and you might get off cheaper than you think.
Cleaning up all the springs/boots would be 2nd on my list.