Just bought this truck. 2005 F150 FX4. I knew it had problems but I got a really good deal on it. 125k miles. Problem is:
When at WOT and rpm above about 3k the engine seems to lose power along with sputtering/cutting out. It only does this while drive. Sitting in park it revs out to redline smoothly. It is not throwing a check engine light. I took it to a friend to have computer check anyway. Threw three codes. One said bank 1 sensor 1 o2 sensor stuck rich. Two said bank 2 sensor 1 o2 sensor stuck lean. Third said fuel pump module offline. So I check fuel pump module thinking it could be cause for other two codes as well. Sure enough back of the module was rusted through and it looked like junk. So it got replaced. Well that didn't solve the high rpm sputtering/cutting out. So currently I have the MAF sensor drying from a thorough cleaning. However, I don't see how the MAF sensor could be the culprit due to it reving out fine in park. I figured I'd try anyway since it was cheap. My only two remaining thoughts are a coil/plug problem, but previous owner said he had new plugs a year n a half ago. Other problem thinking maybe a partially plugged cat converter. Ive scoured this forum for past week and cant find anyone with same problem. Please say somewhere here has had this problem? Any input greatly appreciated.

Edit: I'll report back in an hour or so if the MAF sensor cleaning fixed the issue. Thanks!

 

Any idea what brand plugs went in?

 

No I don't. I could go have a look if you think it will matter. They should be motorcraft correct? I think he said the dealer did it so I would hope that's what's in there.

 

Could I drop out the cats for a test drive without negative effect?

 

MAF sensor cleaning didn't help. As I expected...

 

If it's the cats, they can be tested at a muffler shop. I would suspect plugs or even dirty throttle body.

 

If it were a plug/coil issue wouldn't it miss while in park as well?

 

And/or throw an engine code?

 

Would not necessarily miss until under a load. Moving transmission and weight of truck. Could also be a cracked boot between a COP and a plug. These crack over time due to heat. Misses like this often do not throw a code, makes them hard to diagnose.

 

Do you know that the fuel pressure is adequate? I'd check that if it hasn't been checked already. WOT takes the most fuel. If it runs well normally, fuel pressure is suspect as well as voltage to the plugs and plug condition. I don't think plugged cats would cause missing. I think the engine would not perform up to par.

 

Thanks a lot Patman, Bluejay, and Roadie. I had thought about the fuel pressure too, but is there a way to moniter fuel pressure at WOT? I know there is a port in engine compartment so I could check at idle...but as far as driving and putting a load on it I'm not sure how. I suspect that when the plugs were changed the COPs were not. Is there a way to tell if the COPs on my truck are stock? They have a blueish paint marker line on them. Which leads me to think they are original equipment.

 

When the dealer does a plug change on the 3v engines they usually do not change the cops, so more than likely they are originals. If they did you could be looking at a $1500 bill for plugs and cops.

 

Some great suggestions in this thread.. Having had this same truck for 9 years I can tell you that I had to have the fuel control module replaced as you did, except mine left me stranded on the side of the road.

Has the fuel filter ever been changed? I've seen a dirty filter cause restriction during heavy throttle, although that was my 93 F150. A weak pump will cause these symptoms too.

Like others have said, check the plugs to make sure the right type and gap was used, then check the COPs to make sure there are no cracks or abrasions.

Good luck!

 

noob question. what is COPs?

 

Cops are Coil On Plug