Not sure if this is the place to post .Problem with 2006 F`150 5.4 3v , 81,000 miles . The main symptom is it runs pretty well until you floor it up a hill or go to pass someone?Have pulled codes with only flashing CEL and steady CEL . PO300 , PO306 1st time and PO305 with steady CEL . I am going to throw this out that I think it is the MAF sensor . Because multiple intermittent misfires and #6 misfire and then a week later a #5 misfire does not add up to spark . I installed new fuel filter and I have checked for corrosion on the fuel pump module (ok). So unless the pump is bad and even though it is not showing a MAF error code could it be bad ? I have cleaned it with alcohol . I guess I would need to T at the fuel filter to check pump pressure ? I know they have lots of problems with COPs and Plugs but the symptom is always the dying on full throttle and pulling hills can't get past 55 mph . Sorry so long a post but Thanks

 

Well, it seems to me that we had a similar problem..go check out the link below and it should fix your problem.

https://www.f150forum.com/f4/04-150-...-45mph-298842/

 

A flashing CEL indicates a mis-fire condition. Plugs or COP's ..

 

After reading that other thread I'd start by replacing the Plugs and COPs, seems to have fixed a few guys with the same problem.

 

Had the same problem with a COP. Didn't get the check engine light as it takes over 1000 misfires before it lights up.

 

I understand the COPs and plugs could be bad but when I go up a hill and then get to the top it does NOT run better it continues to sound like a huge 4 barrel carb that is starving for fuel . Even on flat road it will not accelerate if floored .

 

the flooring it part makes me wonder if it could be vacuum related... maybe a cracked intake? My first thought was fuel pump module, cops, or plugs... but i think normally you'd get one cylinder for codes because it seems unlikely that you'd have 2 cops or 2 plugs go at the same time.

 

Well I did a vacuum test it is great and steady , i read on one of the thousand or so forums that a person was having similar symptoms replaced cops n plugs , few other sensors and it ended up being a wire harness was too close to something . I hope to do a fuel pressure check and rule that out , then go from there ! I just cant believe plugs bad at 81,000 miles . Sure sounds like fuel starved to me and if that is the case the maf sensor is the main talker to the computer telling how much air/fuel the engine needs . I have a '65 Chevy Belair 2 dr post with a 496 ci engine and it is 1 of 2 things if it don't start , gas or spark and no computers and boy does it go up hills !!

 

don't make em like they use to..