mrofman

At wits end. Same story as most with my 2008 F150, 5.4 Lariat. 130K miles.
First had slight misfires, no codes. Changed plugs. Changed couple coils. Truck started running worse and the shooting misfire codes. Then running rick bank one codes. Eventually could barely drive it up a hill at 10 mph. Cut out catalytic converter and replaced it. Running much better, but whatever it was that fouled up the original cat in the first place is still there. No codes, but I can feel slight misfire, and the cats getting fouled again. After only a week. The first one was completely broken to pieces on the inside. Could it be something as simple as changing all the COPs, and would I by now need to change out the plugs again? Or shouldI check the fuel injectors and maybe the rail ? This is a tired old question that everyone seems to ask. My god is it ever frustrating. Oh, one more thing. When it had the original cat on and was almost undriveable, I just unscrewed the reader (forgot what its called) going from the manifold to the cat and the truck drove loud as hell, but well enough to take on the freeway. Any advice would be appreciated. This truck beginning to hurt me financially.

Dirttracker18

Did you change COPs after changing plugs? If so, a bad coil will ruin a plug.
Secondly, did you use dielectric grease on the plug boots when you changed plugs and when you put new coils on? This is important as any moisture can cause a misfire.

FWIW it is extremely rare for a coil to fail. What does fail are the spring and/ or boot. An entire spring and boot kit can be purchased for the cost of just one COP.

You need someone with a better scan tool that can see the miss in real time and direct you to a specific cylinder to save you some time.

There comes a time when it is worth paying a high quality technician for their diagnostic time instead of wasting money on parts. Something to think about.

BadFish523

All of this^^^ I would also add what brand of plugs and coils were used? If you can pinpoint which cylinder(s) is misfiring you can focus on a smaller area. ALL of my misfires have been solved with just simply replacing/cleaning the boots and springs and being very careful and meticulous when doing it. The system is kind of picky and if they were installed sloppily then you continue to chase this problem until its done right. Once you understand the system it's actually a breeze to diagnose and fix about 90% of the time.