Looking for advice on how to handle my misfire problem. Took my 2006 F150 5.4L 3V to the dealership to have them diagnose my misfire problem. They test drove it couldn't replicate the problem and found no codes stored.

The misfire occurs usually on a cold engine at WOT condition, like when I enter the expressway on my way home from work at night. The MIL flashes on and off when it misfires but doesn't stay on and once it cleares the misfire it usually doesn't do it again until the engine is left overnight. They told me no codes, they couldn't replicate the problem so I asked them if they could look a little deeper. They talked to the shop foreman and told me it is indicative of spark plug problems, they are hooking it up to some equipment tomorrow AM and he is going to drive it and see what he finds.

I figured it was the plug(s) based on every other 5.4L 3V with a misfire. My fear is that it is the plugs and am worried about them breaking plugs. What route do I take if it is the plugs and they need to be changed and they end up breaking some and try to charge me an arm and a leg for broken plugs?

 

Same exact thing happened to my 06 5.4 3v. It was the coil on the plug of my fifth cyclinder causing the misfire. Definitely get it fixed. After the dealer kept coming up with no codes, it did it long enough for the misfire to eventually cause a fuel problem that ruined my Cat. So that had to be replaced. Then had the plugs changed out(broke 5 of them.......end of story I have another engine now)

 

I guess it took them hooking up some equipment to my truck and taking it for a drive to figure out it needs a tuneup.....quoted me the price of the tuneup, under $300 don't remember the exact price and $40 per plug if any break. Also is getting a PCM upgrade I guess. So much for 100,000 mile tuneup recommendation per the maintenance schedule.

Is the $40/plug reasonable? I've seen a wide range of prices to get the plugs replaced on here.

 

Under $300 and $40 per broken plug is VERY reasonable.

How many miles are on it, and what do you usually use for gas?

 

I've had that same issue on my 05 when the engine is cold. Im thinking it's plug related.