4x4Fun

I have an issue that has me perplexed.

I did my 200,000 mile plug change (5.4L 3V) and decided to do the COPs at the same time as there were issues that others had expressed was cleared up with the replacement of the COPs. I used Motorcraft plugs but aftermarket COPs (yeah, I know, but I had a budget).

After the install, I took a 5 mile trip and everything worked great. This morning, started to drive to work and it started to shudder. I turned around and when I was accelerating from a stop, all was fine, when I achieved my speed, the shudder returned and when I tried to accelerate more, it shuddered worse. I almost thought I would not make it home. The truck did not throw any codes.

I did the test of pulling the fuel injectors one at a time. I found that injector 3 and 8 caused no changes. I removed both and put in the old COPs. Started the truck and it was still rough. I tried the injector test again and only 8 had no change. Okay, so maybe that was a bad COP that was original. I moved a good COP from 5 and put it in 8. Put the original from 8 into 5. Started the truck. The issue was the same. Pulling the injector from 8 made no difference.

Since I had removed the PCM to get to plug 4, I pulled the battery and reseated the PCM connections. I tried it all again and the same issue, rough idle, no change with 8. I am not sure what I might be missing. Just for kicks, I pulled the connection out of the COP in 8 and I did get a P0308 error, so it is doing something. Any thoughts?

ReaperHWK

I just had a similar issue with my plug and spring/boot change about 2 weeks ago. I changed all 8 and the engine was vibrating and missing like all hell. I troubleshot it down to a bad plug. I had a BAD SP515 right out of the box.


I would suggest taking out the plug in the cylinders in question and switching it with a known good plug, were the old ones "good enough" for a test?

4x4Fun

Thanks ReaperHWK! I did not think of the new plugs. I will give that a shot. The old plugs are worn down, but still have a few miles left in them. Now I gotta dig it out of the trash. Sure glad today is not trash day!

4x4Fun

I moved the plug and used what was a "bad" COP to cylinder 4. It is not responding to the fuel injector now. I am going to try an original COP first, but I think it is the plug! Thanks you ReaperHWK!

4x4Fun

Plug swap and the fuel injector was responding. A 6 mile test drive and all is working without shudder. One bad plug and one bad COP. I am glad they weren't together!

redfishtd

Clean them up and keep them . New plugs can be damaged on installation if you don't clean out spark tip holes with carb cleaner . Carbon gets real hard in there and forcing new plugs in there cause problems as well as heat range cooling from carbon around tip . Use a torque wrench
on plugs 25-28 foot pounds ,loose plugs common problem. Use new boots and dielectric grease .

ReaperHWK

Glad you got it fixed, giddy up!