My 2001 F150 5.4L Supercrew check engine light had been on so off it went to the shop. It was starting to sputter under load conditions. They said the
catalytic converters may be spent because the exhaust was not getting by.
Checked that but those were fine. Mass airflow sensor was extremely dirty so they cleaned that but it still ran rough. Got a new one and installed that but still no good. They checked the wiring and everything else they could think of
but still nothing. They even put an alternate fuel source on it to make sure it wasn't a fuel issue. I should replace the fuel filter but at this point I don't think thats the problem. They said it ran better with the MAS unplugged. What I found was at idle it now ran rough but it was better under load conditions and the shifting was not right. Plugged it back in and it runs fine until under load conditions again such as on the highway going uphill.
Any thoughts appreciated. I'm at a dead end.

Thanks
Jeepie

 

Need to know what were the codes on the CEL.
How many miles? And what kind of maintenance has been done.

If you do take it to a shop, try to take it somewhere where they are familiar with fords. Or a certified ford tech.

But a lot of times it can be simple things that you can easily repair such as a bad coil, plugs, vacuum leaks, dirty sensors, injectors, pcv valve, fuel filter, 02's etc... Just need to know what the actual code was. ex: P0300

 

If the engine light came on then there should be a code...Did anyone at the shop think about pulling the code? Sounds like a COP to me.

 

The MAF measures engine load. Older model trucks used a MAP (Manifold Absolute Pressure) sensor to do this. A code does help, as it will make things A LOT easier. A COP problem will definitely cause this sort of problem though, so before you sit down in your pew - find the right church! Get a scan.

 

I replaced the fuel filter, checked vaccuum and the problem still exists. I finally got a code to show up, P0171 and P0174. This leads me to believe it is either a weak fuel pump or some sort of fuel restriction problem. Right now when you drive it feels like the cruise control is set at 45 MPH. Take your foot off the gas and it wants to go. I guess the computer is compensating for a lack of fuel possibly. There is still no power when you step on it. I will hook up a fuel meter and see what that shows.

 

A few weeks ago I posted that 01 screw was running rough. And the problem hasnt stop, only got worse. It keeps fouling spark plugs and giving code p0172. Sprayed a ton of carb cleaner but the engine does nothing different. List of parts i replcaced:
4 new cats
new cop's
new spark plugs ( about 7 or 8 times)
4 new o2s
new egr
new dpfe sensor
new fuel pressure regulator
new fuel seperator hose
new IAC valve
new pcv and crank case hose
3 new injectors
new iat sensor
new throttle body gasket
new throttle position sensor
pretty much over 2500 in parts and this thing is refusing to run correctly. Oh and boight a new maf but it made things worse so i put the old one back on and returned the other. Ive only had this truck for 2 months and the junkyard is sounding real good right now. And yes ive had a vacuum check, compression test, and my injectors checked. Im pretty much fed up with this truck and kind sorry i waisted my money. Does anyone know whats going on.

 

Read this if you haven't already.
https://www.obd-codes.com/p0172

 

Thanks for the site. But that info already know. I put a new maf and it caused my truck to run worse than what its running now. Sprayed carb cleaner all over the engine. And nothing. All hoses that were no good have been replaced. And everything thats happenig, is happening on bank 1 side . The fouling spark plugs on the bank 1 side cylinder 1234. Theres gotta be something thats being missed. A leak thats a big possibility. What about ecm or pcm? Ive heard of them causing problems. Any ideas?