Not sure if these 2 problems are related. I have an 06 F150 5.4 with 185,000 miles (no CEL)

Problem 1: It was misfiring about a year ago and I replaced the plugs and coils, the misfires went away (roughly 35-45mph, when slightly applying throttle to maintain speed, that's when it would misfire). It started happening again so I replaced the coils again because they were aftermarket and I figured maybe they were junk. The misfires got better, but still there.

Problem 2: Just before I changed the coils again, it started idling very rough when the engine was warmed up (it would also run rough and stall when in gear and braking coming to a stop). It seemed like putting it into reverse would initiate the rough idle.

I am not sure if the 2 problems are related, I don't know if the coils I got are junk and didn't help anything or what is going on. I just did an oil change and I run 5w-20. Not sure where to start here... Any help would be greatly appreciated.

 

Are you using Motorcraft plugs and coils now?

You may have low oil pressure at idle, which affects the cam phaser operation. You could try using heavier oil. It may be time for a timing job and high volume oil pump.

 

motorcraft plugs but aftermarket coils.

 

Some aftermarkets are okay, others not. If you don't use Motorcraft, I recommend Denso (who makes Motorcraft coils) or Delphi.

 

Is there any clicking under the valve covers?

 

I don't think so. But I'm taking it to the dealer Wednesday to get a diagnostic.

 

Just fixed all my issues that are exactly what you have. Time for overhaul. See the links to 4 part series on replacement of tensioner, phasers, chains and high volume oil pump