2003 F150 4.6 v8
What is the spark plug thread count in the head on this year 150? Lots of confusing information on the INET about plugs blowing out. One said the threads in the head went from 4 to 8 in the middle of the 2003 run.
If the heads on your vehicle are aluminum there is a changing procedure for the plugs. Run the engine until hot, then let it cool down until you can feel it warn with your hand but not cold. You may be able to get the correct plug by vin number. I believe the engine code on the vin is the 8th position, usually a letter.
Search Ford F-150 Questions
Ford F-150 Experts