Hi guys, I'm new to this forum and have found excellent information and expertise here. My problem is this; My 2005 F150 just turned over 200k and started throwing codes and idiling BADLY. Took it in to a local mechanic who changed the plugs, boots, and MAF sensor. Picked it up and still had the same codes thrown and bad idle. Mechanic flushed the fuel system, no luck. Third time in he replaced the #1 and #8 Ignition coils. Ran good for an hour and started the same thing. Took it in to Auto Zone and they said it read a misfire on the #8 cylinder..which just had the coil replaced. I can do most work on this truck myself but lack in diagnosing. Please help me with any suggestions. Should I replace the remaining 6 COP's? Would that have any affect on whats going on with the #8 misfire?

 

I'd check #8 plug and boot first. Make sure something didnt happen to the plug when they changed it.

 

or swap it to another plug and see if the code follows it...

 

You can get a bad plug even if it is new. And the little rubber boot on the coil could have a split in it somewhere that you cannot see. Agree with the first two, try that first, only so Many things it can be, but one idea, are you sure that cylinder is getting fuel? Clogged injector, or faulty one perhaps? Again, only so many possibilities on a misfire. Good Luck and let us know what you find. That is how we all help, posting not just the problems, but what ended up being the solution too.

 

I'm gonna work on it this weekend. Thank you for the suggestions. I'll post how it goes afterward.

 

My number eight was misfiring and I ended up having to replace the COP because the new one had a crack in the neck and had to replace the plug because the wires to the plug had started to melt laying against an AC line.