hard to create a good thread title sorry. Here’s the story.

As you all know I recently had a misfire bugging me. I took it to a Ford dealer and they diagnosed misfire #6. (Yes, #6. Stay with me). I don’t remember if/what codes were present. They showed me a printout indicatin cyl 6 was dead. Driver side front- should be easy.

So I changed all 10 spark plugs with Autolite brand. Also I replaced the COP boots and springs. Turns out my plugs were factory original (!) and had over 300,000 miles on them, and had worn to over .100” gap and all had crusty stuff on them.

Everything seemed great to the best of my memory. LOTS more power. Honestly I think I had V8 power levels for the last couple years, but now it feels like V10 power
Then after driving a bit I noticed a similar misfire. I was very busy so I ignored it. But it got worse and very annoying.

I pulled the codes and it showed P0305. Passenger side rear. Easy on a van. I changed it with a new Autolite.

Drove around nicely for for a short time but then it starting missing again. I pulled the codes. P0305 again. Ok fair enough- I swapped the coils 4 and 5.

Seemed to run fine for a while and now it’s missing again and showing P0305 again.

*how is it that I’ve replaced the plug twice and swapped the coils, and still have the same cyl misfire? please advise. I want that V10 smooth and powerful again.

 

Then it isn't the plug or coil causing the misfire. It could be the injector or even something in the cylinder. A bad valve, or valve seat, or low compression could also cause this.

 

How old are the coils? I don't even mess around with changing boots or springs, I replace the whole unit because of how inconsistent the misfires are. I gotta change plugs and coils on my boss's V10 van in a couple weeks. I ordered all 8 red coils for $30 shipped. They look identical to the MSD ones I put in my van for $175. I swear they are probably the exact same manufacture. Now I know, everyone's thinking for $30 for all 10 shipped there's gotta be something wrong. But I'm willing to try. The parts store ones are $50 each and they don't last but 2 years and have a 400% markup. I also got OEM Motorcraft platinum plugs for $40 shipped.

 

You have ruled out the plug and COP.
There's also wiring, connectors and the PCM grounding circuit.
Since it's intermittent I would guess electrical.
Something mechanical would be bad all the time unless it can stick.
A wire with a couple of strands left unbroken, a loose connector or a bad chip in the PCM can be intermittent.
Check all the ground cables, too.

 

Did you clear the codes in between? I wouldn't rule out the coils at all. Just cause you moved around the coils doesn't mean anything to me. I've had so many inconsistent misfires that I just replace them all. Even had misfires that weren't on the cylinders coded. I've had some that wouldn't even throw a code but I could feel it was missing only under load.

 

I would look very closely at the connector. Each time you disconnected the COP you corrected the problem for a short time. If you don't find anything, look for a wire that could be moved when you are changing a plug or COP.

 

Like others have already said, check the wiring. Every time you mess with it, it works for a while, and then starts to misfire again. Especially check the injector connector. A little corrosion in it will cause this. Every time you're right there moving the injector and COP wiring, it starts to work again.

 

And! It always runs rough when cold. By cold I mean ambient. Whether 70 degrees or this morning’s 45 degrees.

Im gonna check the wiring today.

 

So it runs rough when first started until the engine warms up?
Idle, accelerating, cruise?
What year, does it have an IAC and has it ever been checked?

 

Op has a van so it is a 2 valve and has an iac.

 

Yeah it has a medium/small misfire at all times, but it runs especially rough when cold.

I checked the wiring today and all is good. Looks good, and doesn’t change idle when I wiggle it.

Today I saw the fuel regulator vacuum line had disconnected itself. 2nd time I’ve discovered that now.
For some reason this web site won’t let me post a pic.
I’ll keep trying.

Im not sure if it has a IAC. It does have some electrical thing on both sides of the throttle body.

 

 

That hose may be shot on the end...are those missing exhaust manifold studs??

 

yeah thats missing studs. I'm a bit concerned about the white stain comings from it. Wondering if it's coolant or something.. that stains coincides with the "unfixable" misfire cylinder 5. I'm hoping it's not some terrible news.

 

must be god's will