well its been doing it for awhile now,it only dose it at1,300- 1,500 rpm under load. but doesn't do it when idling only when in drive.we finally had a engine light come on and it was coil #1 so i pick one up when i went to install it the wire going to the coil wasn't plugged in all the way,so i plugged it in a tried it out no knocking.so i returned the coil.about two weeks later it starts doing again but no engine light this time and all the plug wires are connected good. its a 2002 f150 with a 5.4. so here is what ive done so far.i changed the plugs removed and cleaned the injectors replaced the throttle position switch,and added dialectic grease to all the plug and injector connections.any ideas other than replacing all the injectors and coils(8 injectors will cost me about $800 and 8 coils would be about $500) any help would be great.i tried to find the knock sensor but couldn't locate it.(just in case)also it seems to do it more if im coasting then only accelerate a little to speed up and it gos away if i step on the gas more.

 

Jazon,

My 2003 (83k miles),5.4L had the exact symptom and I have read other questions here that have similar symptoms but differing answers. I took my truck to Gattos and they diagnosed it as a bad coil which also fouled the plug. The tech had a new coil (so you only have to buy one), and began replacing one coil at a time until the problem went away. Sure beats it being a transmission problem!

Hope that helps.

Jim
2003 F-150 5.4L 83k

 

thanks thats what i was going to try next,i think i might even know which one(the one that was half plugged in for awhile)i also changed the fuel filter yesterday day but it didn't help.ill pick up a coil this weekend and let you know if it fixed it. thanks for your help.

 

ok fixed it,some how a piece of electrical tape found its way onto one of the spark plugs,it was between the plug and the coil. it looked like the coil was only touching a tiny bit of the plug.no idea how that would have found its way down in there though?but at any rate every thing works fine now.

 

It is very common for stock coils to break down under a load.

Our new Ford COP’s, the Sultans of Spark(S.O.S.), have
been designed with both durability and performance in mind.
Please see them at:
http://www.performancedistributors.com/soscoils.htm
Quality was the main feature we stressed when we went to the
drawing board on these coils.
By the way, for those of you who only need to replace a defective coil,
our SOS Coils are available separately.