Had something happen while on vacation last week that was strange. A couple of times the truck developed a very hard shudder and a flashing CEL. These spells lasted a short period (5 minutes or so) and went away. The first time it happened was right after the truck idled about 15 minutes, I pulled out and went a mile or so and the "episode" started. Truck was very low on power but would still accelerate. After I got above about 50 mph it just went away on its own and ran fine for the rest of the day and some of the next day. The second time was sitting in heavy traffic for about an hour...very little time over 10-15 mph. Road began to open up and the same thing happened again. Once again a short distance of 50+ mph seemed to cure the problem. Truck has been fine ever since (8+ hours of driving). I couldn't tell if the issue was a misfire or if the tranny was acting up. Anyone else ever had this happen? My only mod is MPT tuning and a cat back exhaust. I changed the plugs at 101k (110k + now) but have still suffered from an intermittent miss when the engine is cold. My Torque II app indicates that cyl. 3 is the culprit. I've changed the COP but the problem is still there...could this be part of the issue? Sorry for the long post, just wanted to get everything that happened in there.

 

misfire, what year truck? Maybe injector going bad and dumping to much fuel while idling or spark plug is bad. I'm guessing u checked the code after it started flashing?

 

My 2008 F150 Lariat did that also around 80K miles.
Only a few times over a 12 month period.
At 90K miles the trans died completely. No forward or reverse.

Swapped it out with a reman trans/convertor from Ford and so far so good.

Ryan

 

Mine done this too me last night on my way home from work. i was going up the on ramp to the interstate flored it to get up to speed and it started mising and bucking bad. Needles to say I just let off it coasted the rest of the way up the ramp and stayed in the slow lane below the post speed limit for about a mile giving it enough gas to keep it around 55 in a 70. Then it settled down engine light went out and ran normal the rest of the way home. I have 128k+ on my 05 still with the original plugs just haven't had much time to change them when working 7 days a week most of the time every once in a while I'll get a sunday off I'm just too burned out to do anything plus with the PITA on the 5.4 I'll have a shop do it if I ever get a chance to get them done.

 

When was the last time you changed/cleaned your air filter and/or fuel filter?

If no codes are thrown then that's what I would suspect. Also try changing it back to stock and see if it still has the problem

 

06 Lariat with 5.4L, 110,000 miles. Plugs changed at 101,000, fuel filter changed 4,000 miles ago and air filter 9,000 miles ago. Only codes I could pull were "Network" codes, both started with U and my scan tool didn't know what they were. Truck has ran perfect since the last episode.