change the spark plug and boot/spring/ all of them if your mileage is up there. a flashing cel is a classic sign of a misfire.

 

Thanks - That did the trick. I had replaced the boots last Feb and had NGK (lithium) plugs in there. Went to the dealer and got Motorcraft (iridium) plugs and all is well.

 

another satisfied customer, glad you got her fixed.

 

So my truck 05 5.4, loses power on load especially going up hill. Saw that I had a misfire on #3 and switch coils from #3 to #1. Since then but cylinders have hit misfire at different times under load. I replaced both coils and the issue still persists if I put to much gas unload instead of easing into the pedal. I recently replace all plugs with Motorcraft plug about 9k miles ago. I've also replaced fuel pump (which was going bad and giving false readings), booster vacuum hose, fuel filter, MAF sensor and fuel control module above rear tire. My next move is to replace both plugs (sp546x) thinking maybe I got.some bad ones. After getting a misfire code the code goes away after the turning the car off and say running into the store and driving away.

 

Make sure the connectors for the COPs are inserted and you hear the click as it locks in place. Sometimes the rubber seal gets rolled up and prevents full insertion. The fact that you now have misfires on two cylinders vs the original one prompted this response.

 

Unfortunately the misfiring is back. Plugs couldn't have gone bad so soon and if so what would be causing it?

 

do you have the DTC's ?

 

DTC = Diagnostic Trouble Code

 

No I do not. It's occurring when I gun it (highway on ramp or fast start from stop). It hasn't thrown a check engine light since I replaced the plugs. As far as mods (K&N CAI, MBRP dual exhaust middle side exit). Otherwise, everything is stock

 

do you oil the K&N filter or is it dry ?