My 04' F150 5.4L with 76K miles engine light came on two days ago and had the following diaognostic code: "PO355 ignition coil E". I pulled all the coils off and tested each one with an ohm meter in an attempt to find the faulty one and they all tested the same. Now the truck is running extremely rough and the engine light is flashing.

2nd diaognostic is coming up the same code. Any suggestions on the cause of my problems? And am I causing more damage if I keep driving the truck?

I have started the seafoam pretreatment process for changing the spark plugs (read from seperate thread) and ordered new spark plugs and extractor kit for a plug switch out as a possible solution. Am I on the right track?

 

Have you replaced the boots on the COPs?

They tend to degrade after time and can cause misfires because the spark grounds out. Also, you need to use the dielectric grease when re-assembling the COP units to make sure you have a good connection to the plug.

 

I did a visual inspection of each boot and they all looked good. I suppose if I replace the boots then I should go ahead and replace the COP units.

I did not mention in my original post that the roughness of the motor comes and goes (happens mainly in acceleration).

 

Why replace the COP and the boot?

If it's just degraded boots giving you issues ($4-5 each), why spend $60-$100 for the COP unit?