A few days ago I took off to work and noticed an unusual vibration and an obvious loss of power during acceleration. It cleared up after a minute or so.
Again this morning I merged onto the interstate and as I tried to accelerate with the traffic I lost power again at 60mph...This time I got a flashing light. I let off the gas and put it in neutral momentarily, shifted back to drive and the light extinguished and the performance returned to normal. Any thoughts? Time to trade maybe? 111,000 miles, recent new plugs and COP. FPDM needs replaced but I sealed it until I can get a new one.

 

Classic misfire symptoms. Pull any / all stored codes, misfire data and address those cylinders ASAP before you toast a cat or two.

Replace a compromised, suspect FPDM ASAP - sealing it is like closing the barndoor after the horse has already left.

 

MGD is Spot on... what brand plugs and COP's were installed ??

 

Motorcraft One-piece. And Accel COP. Will replace the FPDM and troubleshoot the COP tonight. Thanks for the inputs!

 

Pull the codes before you go throwing parts at it.

 

A failing FPDM will not always throw a DTC until it takes something else out... It's already broke open...it needs replaced.

 

Pulled OBD code P0300 and P0304. Cylinder #4 misfire. Cleared code,Replaced COP at cylinder #4 with identical Accel #140003 COP. Marked improvement but still idles rough, I am thinking that this is because the ECM has to relearn that COP. But on way back to work, I got the flashing CEL again. Runs much better especially on hills under load. Is the flashing CEL part of the ECM relearn or should I look somewhere else? All 8 plugs were replaced at time of COP replacement.

 

Accel COPs are a crapshoot at best. Fer reliability, and to minimize that portion of yer life spent chasing misfires, either Motorcraft or Visteon - with proper dielectric application, nw boots & springs.

BTW - which engine is this? The only one-piece MC plugs fer a 04-08 are in the V6's, the 4.6 or late 2008 3V's. All the other use the long-reach 2-piece plugs ( e.g SP515's ).

Change the FPDM - even if you have to use a POS Dorman replacement.

 

To clarify, all 8 plugs were changed just prior to replacing the COP for each cylinder in March of 2014. I paid a local guy to do it based on reputation.

 

Problem resolved!
Got up Saturday morning determined to figure this out. My first thought was to check the plug. I removed the COP and dropped the SP socket down onto the plug. To my surprise, I found the plug to be sitting on the threads but not engaged. Somehow the SP had backed out of the head and was just sitting there.
When I pulled the plug I found that the electrode was gone and the bail was also missing. Also, the porcelain was spinning freely within the metal sleeve.
Replaced the plug and put the COP back on. Started the engine and found it was still missing. It then occurred to me that I had put the original COP that I had replaced on cylinder 5 for troubleshooting. As it turned out, that coil was bad as a result of the broken plug.
Cleared codes and wrapped up the problem. Thanks for all the feedback guys