O.K. to try and make a long story short,here it is....... I have a 2005 f-150 with the 5.4 engine. Bought it new and now it has 107,000 miles on it. Recently,it would have a shudder at 65 or 75 mph then the passing gear would kick on and it worked perfectly. The warning check engine light came on,then,when it acted up it would flash intermittently. Took it in to the dealership and put it on the diagnosis machine. Said cylinders 2,3, and seven were not steady etc?? So,after he took it out and drove it he said those particular cylinder walls were scored. I put in a K-N air filter at about 50,000 miles,and he said that they do not seal properly and dust got by the filter into the intake and got into the engine and did this damage. One think he found was a bad coil on one cylinder and replaced it. And just as he said,when I got on the road home I romped on it and it cut out and the intermittent signal showed again! He said that that would happen and it did. Anyone ever had this problem? He said the cost would be to new heads and 5000 bucks. I need some opinions here thanks Randy

 

A flashing CEL is a catalist damaging misfire . You have a misfire . Hard to believe a K&N would cause that . I hate them but it is not the cause . You need a tune up . Plugs and coil boots and possibly a few coils . Get a second opinion from a good independent shop .

 

I put new plugs in myself at 100,000 miles and I first took it to an independent shop. They had a diagnostic device but not as sophisticated as ford. They agreed on the same three cylinder misfires and thought it was the fuel injectors but said to take it to ford as injectors were something ford replaces on the 05 f-150s of that year up to 125,000 miles. But I agree I will have another shop take a look. That is an expensive answer to this Thanks.