Well my truck has been running fine since the last COP the failed. It was the second time I replaced that COP and my truck has been running normal with no problems or misfires since then. I figured it would be alright to drive 800 miles for vacation but that wasn't the case. The truck start misfiring very little and continued to be very little for the rest of the trip at around 400 miles. It wouldn't misfire if I held it at about 75mph and would only do it if I accelerated slowly. I don't know which COP is misfiring because there is no CEL. I brought two extra COPs (good thing) because I thought it might happen. What would cause COPs to misfire over and over after replacement. The one that I've already replaced twice was the #4, there was no leaking from anywhere and all the wires are hooked up correctly.

 

Update: It seems like a hiccup while I am accelerating but when I get to cruising speed it doesn't do it anymore until i accelerate again. I cleaned the MAF sensor, the IAC valve and I did a spray seafoam treatment and it's still. Am I correct on saying there's something wrong with the COP or is it maybe someting else? I have to drive back 800miles in 8 days and I don't want anything crazy to happen. I'm up for any suggestions for what to do on this.

 

What brand of cop are you replacing them with? And how are you installing them
History of misfire on the cylinder 4 only?
Which plugs are you running and how many miles?
Fuel filter last changed?
How many miles on the truck?

 

The #4 was replaced with a OEM COP, I'm running the ones off of ebay on all the others.
First time the misfire happened my truck wouldn't throw a CEL, drove around for 2 weeks and nothing. I replaced all the COPs and cleaned the MAF sensor, throttle body, IAC valve and changed the PCV valve. Truck ran like new, that was 5,000miles ago. At about 2500 or so it started misfiring and threw a CEL right away, #4, replaced it and it stopped doing it. Fuel filter changed around 10,000 miles go. The truck just rolled over 130,000.

 

Well something I've never seen before.
I pulled the #4 and #1 to swap them and checked the #3 COP and this is what I pulled out. It is plastic and was folded in between the coils and the plug and pushed in the coils. Any idea what the heck? I pulled all the plugs and COPs and non of them have this on it. It was not like that when I put it on there, I have no idea what it is.









The images aren't popping up on my computer, they are in my photo gallery on here.

 

Never seen anything like it. Must have gotten knocked down into the plug well when you did your last change. No other way it could have gotten in there really. It don't look like gasket material. Looks like a piece of harness shell or something. That would definitely cause a misfire if it was between the coil spring and plug. Looks like you found the problem. Make sure that boot is removed and cleaned up, along with the spring. Apply dielectric grease to the inside of the boot throughout and then reinstall over the spring. Then pull the spring out about and inch and clean any grease off that may have gotten on it replacing the boot.

 

I don't see anything ? I looked @ your pics, can't make it out.. Can you brighten the pic up a bit ?



Oh, I see what's going on -

At the end of your picture url, change it from ".html" to ".jpg" and they'll post.

 

Got it jbrew.
Toyz,
I didn't have enough time to do all that today but definitely will tomorrow. It's still misfiring but why would this just happen all of a sudden, if that piece was there before and it was running fine, I don't understand. Also last time I got a CEL and swapped the #4 and #1 I didn't check any other coils. I am going to look over all of them tomorrow and do what is suggested. I'll come back with updates. Thank you.

 

Well looked at all the coils and plugs, nothing out of the norm like that one. I then proceeded to swap each coil with a good one, and run it to see if it still misfired. Each time I did it it still misfired (I swapped one at a time and drove it each time to see if it still was misfiring)
Is there anything else this could be? I did a seafoam treatment and there was almost no white smoke. I put additives in my in my fuel, like techron, gumout, almost every three fill ups. I don't think it's anything with injectors or fuel lines. I put a can of seafoam in the gas tank about a week ago. I treat my truck real nice, oil changes every 3000miles or sooner and am never ragging on it.

 

Go easy on those fuel additives - a bottle of Techron at every oil change is the MOST you should do. Overuse can cause damage and cook cats. I only do it once a YEAR.

Seafoam down the intake can cause issues too - even though it costs money, a BG or Motorvac job is a lot safer. I have that done at every spark plug change.

 

Well it's not always the same one glc but I'll watch it. I did the seafoam after it started acting up thinking it was a sticky valve or something but it's not. It's not missing every time. When I have it in park or neutral it'll idle normal and then miss, idle normal for a bit longer and then miss again. I just wish the CEL would come on so I can find out what it is. Does anyone think it could be a foul plug? They've been in for about 25,000, the OEM motorcraft plugs. When I pulled them nothing seemed wrong with them....

 

Quick question. Could it be the wiring harness that goes to the COPs? I pulled individual caps off the COPs while the truck was running and the only one that didn't make a noticeable difference was the #4. The wires don't look like they are that worn and there's nothing exposed, could it be the wires that go to the COPs?

 

Another question before I start spending money, could this be something as simple as a fuse? and if it is which fuse would it be?

 

Ok so I hook up my tuner(which can check DTCs) to see if there is actually any at all, there wasn't the other day but today I got a 'P0302 : Fault cylinder B' <That's exactly what it said. I know that a P0302 is a misfire in cylinder 2 though. What the heck would cylinder B be? Also why wouldn't my check engine light come on but there's a DTC out there?

 

Well here's what happened. I went with the P0302, misfire, and without undoing the battery this time I changed out the #2 COP..... The truck runs fine now.... What the heck. I cleared the DTCs and it still runs fine.... any ideas on this? I always disconnect the battery when working on my truck and said screw it this time and it worked out....