I have a 2000 v10 X I just bought. Had an occasional misfire, vw ry subtle, when I bought it at Thanksgiving. Had put about 400 miles on it since due to cleaning carpets and panels. Decided to clean the engine bay. Used some foaming degreaser and pressure washed it at the spray bay wash. Not my first time since I ran a car wash for 21 years. Immediately a terrible misfire situation when i started it up. Figured ijt was water in something. Drove another 100 miles trying to dry it out over the next couple of days. No improvement. Pulled all plugs today (autolite XP) and cleaned them, regapped and reinstalled. 7 of the 10 plugs were white on the tip. 3 were brown. Not oem plugs or coils. May be running lean? Put it back together. On start up there is no misfire. Any load put on the engine starts the sputtering. If i accelerate just above idle, runs ok. Sputters otherwise. TB is clean. New filter. What am I missing?

 

 

When I pulled the coil off, it separated from the boot. So I saw the spring, boot and coil separately and all 3 looked ok. Is there any way the boot and and spring could not go onto the end if the spark plug? Like to the side or something while reinstalling?

 

They may look fine but still be bad. You mentioned that they are not OEM. Mine were also replaced by the previous owner with non-OEM coils and at least 3 have gone bad already. There are many threads and posts that tell you how to find which coil is causing the misfire. When you by new coil packs, I'd suggest the Denso branded ones sold from rockauto. They appear to be OEM with a Denso sticker covering the Ford part number and they cost a fraction of the price that the dealer charges.

 

Looking at the Denso 6736000 COPs on ebay and Rock Auto, they come with the straight boot. All the ones on my X had the slant boot like the 3V triton has on my Expedition. Do you think the slant boot is causing issues?

 

Being the incorrect parts would make me a little suspicious as to them causing the miss AND the previous owner's work on it.
Are you fully aware of the earlier heads low thread count and all of the precautions and torque needed for better longevity of new plug installation?

 

I have been reading about the torque specs. I am stumped that it ran fine BEFORE pressure washing the engine bay. Then like crap!

 

And no CEL light whatsoever.

 

Based on the photos on rockauto the 2v v10 has the slant boot a d the 3v has the straoght boot. I didn't always get a cel when I had a miss either especially when it was intermittent. I used a Bluetooth obd2 adapter and torque pro to see which coil was missing.

 

I have had issues with moisture in my COPs after washing my engine bay. Get a code reader and read the temporary codes. It will tell you what cylinder is misfiring. If it were me, I would replace all 10 plugs and boots and replace any misfiring cylinders with new coils.

Check injector clips. They are old and brittle. Loose connection will give a misfire.

Good luck!

 

I would start by checking all of the connectors, high pressure will put moisture in all sorts of places. Get them all clean and dry, and see if your miss fire goes away. If I were a betting man, I'd say you probably have several with moisture in them.

 

^^^ Once again this ^^^ get a good reader