So I have been having all kinds of problems with my truck. Horrible milage, rough idle and in the last week my check engine light came on. I got codes P0300 and P0301. The problems have progressed but got worse the last week or so. I changed plug wires, o2 sensors and a couple vaccum hoses that were rotting thinking I might have a vaccum leak. Also check the coil pack and resistances all checked out ok. I never did change my spark plugs though because I changed them only 3k miles ago. So yesterday morning the truck goes into the shop.

I get a call about 2PM and the guy asks me "do you do your own maintenance"? I'm thinking oh no.... He then scolds me as I'm sure most will do with responses to this post. He says "Never, never, never put Bosch spark plugs in a Ford engine, you have 3 bad spark plugs. You have a Ford, only use Motorcraft plugs".

Wow, talk about feeling like I was in trouble. BUT... I felt like others could probably learn from my mistake. They changed the plugs and cleaned the intake/combustion chambers and I swear, the thing runs better than it did when I bought it.

I also did some digging after I got off the phone with the guy, found out there have been many threads about this topic. I just didn't look hard enough. So after getting about 10-11 mpg for the last couple months, it appears that my milage problem has dramatically improved along with power and idle. When I go through a full tank, I'll post my new milage here. But for anyone having milage problems make sure you are running MOTORCRAFT plugs.

 

10-4.

Motorcraft are the best bet.

And, I have had equally good results when using Autolite copper core plugs.
(work fine, just don't last as long)

Bosch plugs just don't seem to be the ticket in Ford engines.

Glad you got it squared away and thanks for posting.