Im new here and need some help. I got a 2002 F150 5.4 4X4 with a p0308 mainly between 1300 and 1600 rpm. Ive done normal maint w/ ford coils and plugs and also injectors. Still comes back. Any help will be appreciated. Been chasing this demon for over a year.

TIA

Mindwrpr

 

Check compression.

 

Did you do all of this work, or have it done by a shop ?

Just to clarify, you replaced all 8 plugs, coils, and injectors? And all with new motorcraft parts?

 

Did it myself. Have some automotive knowledge. All motorcraft parts and the problem was happening before the maintance service.

 

Check for a lean miss due to a vacuum leak or low compression for cylinder # 8. Also look that the # 8 fuel injector is being properly signaled.

 

Check and make sure the electrical connector for the injector on #8 is attached fully. It should "click" in place when properly connected. Sometimes the connector's internal rubber seal gets rolled up and does not connect properly.

The following is from a post I made a couple of years ago.I recently replaced a COP in my 2007 F-150 STX 4X4 4.6L extended cab and had an issue getting the connector to lock onto the COP for cylinder #8. Inspection found that the rubber O‑ring (reddish rubber seal) was ripped and preventing the connector from seating properly. I used a pick but could not get the seal out of the connector as it was deteriorated and falling apart instead of extracting in one piece. The annular space in the connector would not allow pick to enter 3 sides. I had an old connector sitting around so I inspected it to see if there was an alternate method to remove the seal. Inspection revealed that there is a very thin slot, about 1/8” wide and 1/64” high that provides some access to the back side of the seal as it sits inside the connector. I tried all sorts of tools to get into that slot but nothing was strong enough to push the rubber out of the connector until I remembered that windshield wiper blades have stainless steel reinforcing that is about 1/8” wide and 1/64” high that might do the trick. I took apart an old windshield wiper and removed the two SS reinforcing. Using one of those pieces, and with some difficulty, I was able to push the remaining portions of the seal out of the connector, and the red plastic conductor separation plate came with it.

I put in a used, but serviceable, O‑ring seal into my existing connector and then reinserted red plastic conductor separation plate into the connector. With the new O‑ring seal the connector locked onto the COP.