So I recieved a check engine light on my 99 F-150 4.6L truck. The code was P0307 for a Cylinder 7 misfire. I changed all of my plugs and wires and drove it to O'reillys to delete the code. I got almost home and it coded again and started shaking. When I popped the hood the wire to cylinder 7 was in the hole but not pushed in all the way. I thought it might have been a mistake on my end and drove it to work today. Half way to work it started sputtering again and coded. Once at work I popped the hood and the boot was disconnected from the plug again, althought the boot was still in the hole. I pushed it in again and it ran fine. Has anyone ever had this happen to them? What is going on? Please help me.

Side notes: the wire is long enough and there are no moving parts that are pulling on the wire while it is running.

 

Defective wire?

 

Did you put dielectric grease in the boot? If you put to much in it is hard to get the boots to go all the way on.

 

I did use dielectric grease on the plug but a very thin amount. I am starting to think it is a defective wire/boot.

 

RE TORQUE your spark plugs, the happened to me several times when ford did my spark plugs the first time. If the spark plug is not tight it will cause blowby, or the spark goes around the spark plug causing it to to pop the boot off, best way to check for blow by is to put your finger on top of each spark plug boot while the engine is running, if you feel a pulse that plug is getting blow by