I have an f150 that has had lack of power issues. It is a 2010 flex fuel crew cab 4x4 with 177000 miles on it. I had the cam phasers replaced at 145000 miles because they went out, but now im fighting another issue that no one seems to know the issue. I have taken it to 5 mechanics and they all have hooked it to their computers and said that i had a lean code on bank 1 upstream o2 sensor and bank 2 upstream. The new parts I have put on since this whole issue started are new spark plugs and coil packs, driver side cat converter, driver side o2 upstream sensor. The passenger side cat looked good is what the mechanic told me. When i accelerate hard the engine bogs down and accelerates slowly until it reaches 45 to 50 then seems to pick up. It also bogs down when going uphill. I read somewhere that if you have your truck running and unplug the mass air flow sensor the engine will die, so i did that and the engine didnt die. I would of thought that if my mass air flow sensor was bad one of the mechanics would of seen it on their computers. The mechanics all did fuel pressure test and it has good pressure, and they also made sure the exhaust system was free and clear of debris. Im tired of spending money on labor just to find out they cant figure it out so please any advice would be appreciated.

 

Just throwing a dart at the board... but possible fuel pump issue?
Have you noticed any loss in mpg's?

EDIT: Ah, just re-read your post. Fuel pressure is confirmed good? Did they also perform a volt test?

 

There was a vid kicking around on YouTube that guy had mystery power issue with his f150 and ended up being a piece of foam came dislodged in body panels and clogged most of his air intake (inside fender by air box).
Was a head scratcher why the foam is there ( maybe used in assembly)

 

 

Also Ive tried cleaning both the MAF and the throttle body. How do you check for a vaccum leak?

 

• Visual
• Sound
• Starting fluid

 

I just sprayed starter fluid on all my hoses and didnt hear anything or hear the engine pick up from spraying the starter fluid around vaccum hoses and around where the air filter is. Im just stomped and no one seems to know either.

 

Almost sounds like Exhaust system has a restrictionBut mechanic was sure that there was not any restrictions. You could always try to install Performance custom tune from five star like I did several years ago and in your case will benefit from the cats set to permanent not ready and maybe ur new strategy in the pcm will correct the lean power condition and get power back. The downside for me is I have to return truck to stock to pass state emissions every 2 years but the performance gain with tune is worth it especially on the stock 5.4 ( they seem under powered from factory LOL).

 

What spark plugs? Are they gapped correctly? The 5.4 shouldn't be as touchy as the later engines, but if they are offbrand it could matter.

 

I put champion double platinum sprk plugs in it. I looked online and found the gapping standard and went off that. Sitting at idle the truck doesn't seem like its misfiring. I do have an exhaust manifold leak due to the back two bolts snapping off on passenger side. I dont know if that would cause it to bog down going uphill and passing.