I have a 2006 f150 5.4 triton. And a couple of months ago my truck started to stutter around 40-50 mph but it would only do it sometimes. So I didn't think anything of it besides it misfiring so I replaced a couple of coilpacks one by one as they were going bad. And just yesterday my truck started to misfire really bad in cylinder 3 so I replaced the coil pack and every spark plug thing that would be it well it wasn't. Does anyone have any idea what it could possibly be. Please help

 

How many miles on it? Did you use Motorcraft plugs? How many cops did you change and what brands did you use? Did you use dielectric grease?

 

143xxx and yeah I used motor craft 515s and I've replaced 4 out of 8 so far and duralast cops and no grease

 

Problem #1: Duracrap COP's

Problem #2: no dielectric

Note that it could be something valvetrain-related for that specific cylinder as described in this thread: https://www.f150online.com/forums/v8...-problems.html

MGD

 

If you can get your hands on a code scanner, pull your codes.
If you can't, then find your misfiring cylinder by unplugging your fuel injectors one at a time. Each time you pull one you should hear and feel the idle drop and the engine get rougher. The one you pull that makes no difference is your misfiring cylinder. Now you need to figure out if it's the COP, the plug or the injector not firing.

 

I've had 2 misfire situations...neither showed on my Actron Code Scanner...

One took the dealer weeks to figure out (Cyl #3 misfire) because it felt like a transmission thing..., and Cyl #8...
I was able able to get it to misfire soo bad that it finally gave a check engine light and code for cyl #8...took a test drive on a long straight empty road to do that...

I personally am starting to get another misfire, but is very random...occurs when truck shifts into overdrive, and RPM's drop...which has been the case with the other 2 misfires...

I have replaced 7 coils with BWD's from O'reilleys. They have about 50k miles...one was replaced with a motorcraft from the dealer,, so I didn't change it...it has about 60k miles on it...

 

How many miles on what brand plugs? Did you use dielectric grease on the cops?

 

I have a 07 and have been having this problem for the past few days without getting a code. Finally today I drove about a hundred miles and I got a code, misfire on cyl #5. I just had Ford replace the plugs a few hundred miles ago. I'm going to move a COP from another cyl and see if it's the problem. I'm hoping it is.

 

If it feels rough at idle, try my advice above.

 

Could it possibly be my tps? And yesterday on my way to work it was bucking and backfiring and once I left work I couldn't get it to do it I could get a code to pop up I drove it for a half hour so I put octane booster in and filled the rest of my truck with premium l and changed the fuel filter I am seriously so dumbfounded on what this could be I have been looking up a bunch of stuff and it's all different

 

Octane booster is not what you need - you should use Techron. No codes?

 

Well I had a can of seafoam in my tank I drove it down to a quarter tank and I did the seafoam straight through the vacuum lines and no there hasn't been any codes

 

Seafoam through the vacuum line also doesn't help with anything fuel system-related, and it can damage the converters. Again, use Techron in the tank.