This is my question;
What causes the coils that go over the spark plugs to go bad?

So I was driving home yesterday in the V10, and as I was getting off the freeway, my truck started to sputter (like a misfire). I had my predator with me, and sure enough cylinder 4 was misfiring. I replaced the coil and the truck ran fine until this morning. It started doing the same thing. I plugged the predator back in, but this time it was registering cylinder 1 as misfiring. I was worried, because yesterday when I replaced COP 4, I removed COP 1 to compare the two (I was having troubles getting COP 4 seated). But I only had COP 1 removed for a short time.

So anyhow, this is where I stand now. I replaced COP 1 and COP 4, but now the truck is still sputtering. It ran great for like 5 minutes after I replaced COP 1 today, but then acted up again. It will misfire intermittently at idle, and when I accelerate up to around 2000-2200 rpms. Above that, It runs just fine.

I'm not sure which cylinder is causing the misfire right now cause it hasn't yet registered on the computer. Which is weird cause the other two registered immediately. I hate throwing parts at stuff, I just wanna figure out what is going on. I'm working on getting the predator to tell me which cylinder is misfiring. When I find out, I'll post it up. Thanks in advance.

 

A couple of things. Coils do fail over time no matter what has happened to them, their lives are limited. What killed a couple of mine was water getting down in the hole shorting out. Rotting/Cracked boots can allow the spark to jump to the cylinder head rather than the spark plug.

I suspect you're working on the 2000. There was a problem with some of the COPs on the earlier engines. As I under stand it, in 2003/4 they were changed or ford changed the manufacture and all was better with them. Your truck is a decade old anyway, so changing the boots should be high on the priorities, they have a service life similar to spark plug wires.

 

you may want to pull the plugs too and make sure they're not fouled. you say it goes away at higher RPM's, and a partially fouled plug will do that.

 

My 99 F250 V10 was missing also at idle. Check the vacuum hose that goes from the pcv valve to the throttle body. It will more then likely have a cracked , split or dry rotted hose usally right at the elbow where it goes into the throttle body.

 

Heat, vibration, water, and spark plug blow out or improper installation are the four biggest COP killers. Also time. Even if all situations are good, they have a shelf life of around 100K miles. You get more than that out of them and you are doing good.

 

It was cylinder 1 that was still misfiring. Finally got the code up on the predator.

I pulled that plug on cylinder 1 and it looked remarkably in good shape. That was my though too, maybe the plug was fouled.

I checked that, it looked in good shape; for now.

I am planning on replacing the other 8 COPs here real soon. I just landed a job at Summit Racing, so I'm planning on making them one of my first purchases.

Well apparently something wasn't seated right. I unplugged and greased and then replugged in all the connectors to both the COPs and spark plugs at the harness on cylinders 1-4. Whatever I did made it work. Lets just hope its fixed until I get all new ignition (plugs, COPS, and maybe a harness)

Thanks for all the input guys. I appreciate the help!

 

Good deal, and congrats on the new job! BTW, the boots are also known to split on the OEM COPs. Changing an $8 boot can sometimes fix the problem that most think is a bad coil. Glad you got it fixed.

 

Thanks very much! I'll keep that in mind when I look at them next; $8 is much more reasonable than 43 for the entire thing from Azone. If the boot splits, does that mean the problem is the spring making contact with the wall?

 

If the boot splits the spark will find its way to ground (shortest path to least resistance) and not to the plug therefore causing the miss.