Over the last few months my 2004 FX4 has developed a slight "Misfire" while idling. Truck has 160K+ miles and the plugs were changed around 120K miles. The other day I popped the hood and started unplugging COPs while running. Only 3 or 4 of the 8 made it run rough when unplugged. The others I unplugged made no difference which leads me to believe that I have some bad COPs. Can anyone chime in and confirm my suspicions?

 

When the plugs were changed were the boots replaced, too?
The coils are probably fine, but that's a lot of miles for the boots.
I've been using the NAPA 702418 boots ($6.30/ea) with no problems
You might want to get an OBDII bluetooth adapter and software (under $50) to determine which cylinders have pending misfires that don't set codes.

 

No the boots were not replaced

 

I removed a couple of the front cops and the boots look fine. I notice that it's worse when the motor is could. There is a slight hesitation when accelerating and then I feel it start to pull harder.