2004 F150 134000 miles. I was getting a misfire on number 6 so I changed the plugs ran great for a day then I get error code p0174 an misfire on number 1. I checked for vacuum leaks dont see any soi clear the codes. drove a block down the stop it idles rough when in gear and the brake is pressed scanned it misfire on number 5 clear the code. ran good for about 2 days now now I have p0174 p0345 and p0351 clear it comes right back. so it idles rough when in gear and the brake is pressed and runs rough at about 35-50 mph any help would be great

Thanks
Dale

 

My 2004 5.4 3v F150 is doing the same thing. Some time back I replaced all the sparkplugs which was a learning experience. But now my CEL either flashes for a little bit or stays on. Sometimes the whole issue goes away and the truck runs like a stallion. I need help!

 

Most likely one ore more COP's (Coil On Plug). The FORD COP's can have a a low grade misfire issues when they go bad. They many times don't stop working totally, they just don't work at certain RPM's, Loads, Speeds, At idle, At WOT.....