2003 F150 FX4, 5.4 with 102,000 miles. Truck has never given me any real problems, fresh motorcraft plugs & coils at 100,000 miles. Parked the truck last night & everything was fine, today I start it up & the idle is a little rough, nothing drastic, but not as smooth as it was. Start driving & I noticed the acceleration also not as smooth as it was and service engine light is also on now. Opinions? Thank You!

 

Step one is to get a scanner and pull the DTC's. Anything else is just shooting in the dark with the parts cannon.

 

Super simple stuff to keep in mind while you're planning would be bad fuel (did you fill up recently?), gas cap popped loose (mine has done that), coil came loose (maybe the mounting screw fell out), spark plug loosened up or was improperly torqued. Cracked spark plug causing a misfire. Somebody just mentioned that in a different thread. The COP system coils needs a good tight seal around the plug or spark will find a new path.

Just some things you can check easily that might give a sudden change, considering also the recent work. p.s. who did the recent work?

But a code read at least before you take anything apart. Good luck.

 

I replaced the plugs & coils myself, all genuine Motorcraft stuff & torqued all the plugs to 24 ft. lbs. & everythings been great for the last couple thousand miles.

 

Are you sure they were genuine parts? There are a lot of counterfeit Motorcraft parts on Ebay and amazon.