buck91

Been chasing this problem for a long time, initially it felt like two problems; a shudder on take off and a miss on the highway. Well after playing the dealer game I took it on myself (as usual) and managed to SIGNIFICANTLY reduce the problem with new plugs and a couple tanks of fuel cleaner (yeah yeah, but it did improve a lot after that!). Now its to the point where its barely noticeable, mileage has improved and I could live with it. Problem is, its still there most of the time. Really feels like a light misfire during take off and while at cruising speed on highway.


Originally was diagnosed using mode $06 as no CEL has ever been tripped. Showed misfires on #8 and random other misfires. All plugs except 8 looked great, but were too wide and #8 was black and sooty and too wide.


I want to pull #8 again to inspect, but other than that I found a COP boot on ebay for the 5.0L, so I'm going to swap that out since its cheap, easy, and historically has been a known trouble spot on Fords. Also going to open up the intake to give the MAF a little cleaning just in case its a factor.


Has anybody run into misfire problems on the new 5.0L? Service manager and I were in a long conversation about it a while back and he was very surprised saying he never sees any issues with the newer 5.0L's.

Ford850

You'll see the occasional post on here, for any of the engines, with symptoms like yours. Usually it is a cracked plug or bad coil.