I recently bought a 2007 F150 with the 5.4L engine and 65k miles. I test drove it and everything was fine no problems. I paid the guy then as I was driving it back to my house it started to misfire when cruising above 40mph under light throttle. The CEL did not come on. I made a couple calls and a friend said it was likely a bad ignition coil. So I bought a coil and replaced it in each cylinder until it seemed like the problem was gone. I though this had solved the problem because I wasn't able to make it misfire. That was about a month ago, now recently it started misfiring again under the same conditions. I assumed that another coil went bad so I bought a whole set and replaced them all. I tested it out this morning and I'm having the same problem. It seems as though it gets worse sometimes and others it is hardly noticeable. It is only when cruising above 40 in top gear at low rpm and light throttle is applied. Any ideas on what may be causing this? Are there any computer updates or anything of that nature that could be causing this?

 

I would replace all the coils. go to e-bay and search "DG511" Global is selling them for under $120 for a set. Might want to do the plugs at the same time.

 

Found a place locally that sold them for $104, but that didn't solve the problem.

 

Get the spark plugs changed. Even new coils have a hard time firing worn plugs under those conditions.

 

yup sounds like the plugs, use MotorCraft

 

x3. Had the exact same problem and it was a plug.

 

is motorcraft the best? i know ford recommends them, but they also say never lift your truck or put larger than stock tires on it either. lol...

 

Ok thanks for the help. I guess I'm going to bring it by a stealership today and have them look at since I've heard dealing with the plugs can be a pain in the *** anyways. A little early for the plugs to go, but I hope that is the problem.

 

Was that each? Global sells them $120 a SET(8)..

 

$104 a set. Its abcmarts on ebay. They were local so I saved the $10 shipping.


Well was told today by the stealership that my plugs are bad. Mechanic said it was misfiring randomly on all the cylinders and slightly favored one side possibly indicating a bad cat on that side as well. For new plugs, cleaning injectors and updating computer gonna be roughly a grand....Then if the cats are bad thats another 1800 a piece, which are on backorder. And the best part is they are not responsible if they break a plug off when changing them out, I am responsible for the labor on removing the broken plug.

I have a hard time believing that all my plugs are bad with only 65k miles. Going to get an unbiased opinion tomorrow from a service manager at another dealership who a friend of mine knows.

 

Man 1800 for cats. That's unbelievable. If one is bad i'd call muffler shops and delete the 4 cats for 2 high flows. Recycle the old ones and it will help pay for them. You can do that for way less then 1800. Dealer charged me $200 to install plugs I bought on the internet awhile ago in my van. That's one way you might save money. I'll have to look for that abcmarts.

 

the 2007's only have 2 cats. 2006 and later i believe

anywho. yea i went into the ford place with my ranger one day, no cats, they said that was the problem and they could put a new converter for 1500. i said uh NAH! thats not the problem bud! then i couldnt pass inspection so i got a converter (catco brand maybe?) put on for 150

 

The going price for a 3v plug change should be about $350 plus $80 per broken plug. A full injector and intake cleaning should be less than $150. Cats should be on warranty!

 

my thinking as well, what is it 80k miles? and like 4 years or something like that

 

8 year/80k.