I have a 2006 F-150 Lariat Super Crew 4x4 with the 5.4. When I bought the truck, it had a cold air intake on it and a magnaflow exhaust system that exits on the passenger side of the bed. I have a miss in the truck when you get on it, but as long as you are just cruising, it runs fine. I sent the truck to my local private ford mechanic to diagnose the miss and go ahead and change the plugs. (Ford wanted $646.00 for a plug job and $100.00 for each coil pack that would need to be replaced) The mechanic had a plug seize up and break in the head, so $121.00 later I purchased him the Lisle tool to save me from sending it to Ford to extract the broken plug, $406.00 later, I had 8 new autolite plugs and one new coil pack. He replaced the pack on the #5 cylinder which took care of that cylinder missing, but the #3 cylinder still misses when you get on it. He swapped some packs over to see if the miss followed the moved pack from the 3 cylinder, but it stayed at #3. I spoke to another person who bought an identical truck to mine, almost the same problem, he had his cat replaced, and it fixed his miss. According to him ford wanted apx. $4000 to replace the cats. An exhaust shop quoted him $700 for each cat, and told him it had 2 that needed to be replaced. Luckily his was still under the emissions warranty, and it sat at a ford dealer for 2 months waiting on the parts and job to be completed. My truck has sat at the mechanics shop for a month waiting for them to finish diagnosing it, and I went and stole it back this weekend to move some furniture. When I left the shop, on a rural straight road, my computer displayed the mpg, and it topped out at 16.8 mpg; before I did good to get 13.1 on an interstate. I was excited about better mpg. Over the weekend, My mileage got back down, and stayed between 10-12.5??? Also while driving it I could hear a loud whistle sound while accelerating??? I come from a Ford family, and drifted off course, and went from driving fords to 2 GM trucks, got smart and went back to Ford. I am starting to question whether I got a lemon and whether the Fords being produced now, are as durable as the fords produced up into the mid 1990's. I looked on the net to find some injectors, and found some, but I am unsure as to what color stripe my year and motor require. If I can get some injectors, the I will plug and play to see if the injectors are causing my miss (I am hoping that it will). What else could be causing my terrible mileage, misfire, and whistling noise? Please Help!!!

 

I was also told that there was a customer service injector recall by someone who had their injectors replaced under this recall. I searched the net for that and only find that to be active on the 05 5.4's? I also called Ford, and they played dumb and told me they were not aware of any such extended warranty or recall on 5.4 injectors....

 

maybe a vacuum leak somewhere

 

Just recently I made an 80 mile round trip to haul a lawn mower on a trailer, I started my trip with the empty trailer (14ft with mesh gate). On the interstate, the truck would not pull grade, it was like it lost power. The RPM's stayed about 2200, my mileage went to 9ish, and on any type of hill or grade, the truck would get passed by semi's that were governed at 65, and before the grade I was running between 75-80... No buck-jumping or misfires, no rpm increases, just no power on grades...