So I have put about 5k miles on my 03 V10 since I bought it last September. It now has 212,000. When I first bought it, I had a CEL on with code P0360 for cylinder 10. Changed the plug and coil/boot with a Motorcraft. I also went ahead and changed all the plugs just to check them out and it was relatively inexpensive. Then about a month later another misfire on #5. Then a few months later another on #1, then another on #6 a few weeks ago. Today I had another #6 misfire on a Motorcraft COP that was less than 3 weeks old. So I changed the coil/boot again. I went to run an errand right after changing the coil on #6 and I get a CEL of P0360!!!! #10 is now misfiring 2 mins after I changed #6??? WHAT? It wasn't misfiring 20 mins before, but now it is? Come on man. I cleared the code in parking lot at Home Depot and drove it 5 miles home and code didn't come back and it seemed to run fine. So that is kind of weird. Clearing a misfire code and then the misfire went away???? So in 5k miles, I have changed 5 COP's. I had 3 Toyota trucks from 1999 until 2022, all with high mileage and never had to change 1 COP. So something is going on. Starting to think this could be fuel injector or fuel pressure/pump related. Not sure. Anyone have any ideas?

 

What is the condition of the COP connector?

 

All connectors look good. No corrosion or frayed or pinched wires.

 

Are all of the COP electrical connectors fully intact, even the tiny locking tabs?

Has it been raining during or just prior to these misfire events?

 

Pins/tabs are fine. No corrosion. Hasn’t been raining much around here.

When I first felt the miss start Monday, I had just filled up tank. 35 gallons went in at Walmart/Murphy’s. Which is about normal. It was a just a slight little miss around 1300 rpm. By Wednesday it was missing bad, like real rough running at red lights etc. Never stalled though. RPM’s stayed pretty steady at 700-800. Scan today said #6, which pissed me off bc I had just changed it at end of August. After I posted this thread I drove it about 20 miles to Advance Auto and it ran fine. The code of #10 hasn’t come back. I put two bottles of injector cleaner in tank then drove home. Could bad gas cause this? I just can’t see any issues with coils. Boots all look good, no corrosion on spring and plugs look good.

 

Tomorrow I’m going to clean and test my battery. I did notice some corrosion on the post and clamp. Eliminate that. I’m also going to try and check the COP I removed from #6. I want to see if it’s even bad. I suspect it isn’t.

 

So this am I tested the COP I pulled from #6 yesterday.

primary getting 0.6 ohms
secondary getting 5.62 ohms

I believe those values are with the correct range for a good Motorcraft COP. Can anyone confirm that? Not finding much on my search.

 

I suspect you are not having issues with the COPs.
Can you feel the misfires either at idle or under load such as when accelerating?
Also, it seems coincidental that the V10 firing order starts with 1,6,5,10,.... and it is all the cylinders on the ends of the heads.
I think I've seen this in another thread awhile ago, but I don't know if the cause was found.

 

That is pretty interesting. I feel it the most at 1300-1400 rpms when I’m accelerating. Just normal acceleration to get to 55mph. Also when cruise control is set at 55mph and going up overpass.

I drove yesterday about 50 miles and it ran fine. No misfiring. Maybe the injector cleaner worked. Will update as I continue to burn this tank of fuel down.