I have a 2006 2WD F150 XLT. Truck runs like its running out of gas once I hit 2100 - 2300 RPM's. Will idle forever. A P0191 code was being thrown so my mechanic REPLACED BOTH FUEL FILTERS, FUEL PUMP, SPARK PLUGS, FUEL PRESSURE SENSOR AND THE FUEL PUMP DRIVE MODULE. The problem has not changed. Called the ford dealership and they said, "change the coils." Mechanic never did since the problem is i am losing fuel pressure. The pressure went from 30+ PSI to 6 PSI when it hit 2100 RPM's. Fuel regulator was not replaced, but I have already put in $1400 in this... Any suggestions.... Oh yea. The other code is P0446 (evaporative emission system).

 

Which engine?

 

Right, need the engine size.

Huh, -why wasn't the regulator replaced ? Could be flaky. Also, attempt to start, key on and feel the pump relays. Are they warm or hot to the touch? If so, they're bad.

 

If its got a FPDM it shouldn't also have a regulator, it should be a returnless fuel system

 

Oh sorry, Probably the most important part. It's a 5.4 Triton V8. I went to auto-zone to find those 2 codes. The reason I brought up the fuel regulator is because it was something that was recommended to fix the problem on their recommendation. Wasn't too sure.
Something New: Just took my truck to a different mechanic. This time, I could not get it there without having to restart the truck over ten times in a 5 mile distance. The truck started up just fine. In Neutral, the truck will hold at 2500 RPM's no problem. Once in drive, it was choking as if it were running out of fuel if it went above 1500 RPM's and die, but would idle somewhat fine. Won't die in an idle. Once it acted up, I would turn it off, restart it and would be good for about 1/4 mile or less and do it again. Worst it's been since the problem began.

 

Does it make a sucking sound when you remove the gas cap?

It's just a guess, but with the P0446 you may be causing a vacuum it the tank and causing the fuel flow to be restricted. I guess you could try running it with the gas cap off and see if that helps. You will/should get a code running it with the cap off.

This is just a wild **** guess, but worth a try.

 

Why didn't they do a fuel pressure test? You check your vacume lines for leaks?

 

No sucking sound with gas cap. When I did some research on the P0446, someone had this code pop up when they started the truck with the cap off and it went away in time. I will try it though. The mechanic did do a fuel pressure check, "The pressure went from 30+ PSI to 6 PSI when it hit 2100 RPM's." He had to place a custom made valve in the line to be able to hook up his pressure tester. The new mechanic mentioned that he checked the truck yesterday. Just waiting a response on what he finds too. I will fill you all in with his information.

 

6 psi ????? Ding ding ding....

 

Put it this way and from recollection without looking specs up. The fuel rail MUST maintain 29 psi at minimum for the engine to function. The 29 psi is two valve spec, so the 3 valve spec might be higher than that. Coming anywhere close to 6 psi WILL STALL the engine. Sounds to me like problem is nothing other than fuel delivery.

This is simple to figure out just from your post. Why the mechanics haven't is the more puzzling issue.

 

That's hard to figure, being that you have already replaced the filters, pump, sensor, and FPDM. There is no regulator, the FPDM handles that.

 

That doesn't really matter. Since anything could be bad out of the box. It's looking that way.

 

Ok Everyone, I want to thank you for all of your advice. I had just received my truck and it seems to be operating properly. I will give you a quick recap with the conclusion.
My truck was acting like it was running out of gas. It would only do this on a half of a tank. Took it to a mechanic who replaced the pump.
After that the problem got worse. He did a fuel pressure test and found that the truck loses pressure at 2100 RPM's going from 31 PSI to 6 PSI.
He then replaced both fuel filters, fuel pressure sensor and the spark plugs. Truck ran worse after this. He called Ford and they said Fuel Pump Drive Module (FPDM) needs replaced and the coils. He disagreed with the coils but replaced the FPDM. No luck. He then told me he gave up and to take it to Ford.
I took it to a different mechanic who did another pressure test and a voltage test on the pump. showed the pump with 13 volts and low pressure. He determined a defective fuel pump.
After removing my gas tank, he noticed that the tank and gas was horribly dirty, and vacuumed it out. As he began to replace the pump, he also discovered that the pump was installed improperly and the filter was really dirty.
After all this was replaced and $2200 later, the real issue was a $450 fuel pump that was defective from the factory and installed improperly.
I hope that this helps people in the future.

 

The lesson is sometimes its just better to let the dealer do it the first time. Unless you are super confident in a mechanic you know. They dont have fuel pressure zerks anymore because you can read the fuel pressure off the computer..

 

Yea, like I said, -it was looking that way. Defective out of the box isn't that uncommon. I'm not sure how you would install a FP improperly ? Wait a minute, there is something and with your description, this is what I think MIGHT have happened. The fuel pump was replaced, but the new pump didn't come with strainer or sock as it's called. So the old one was used.

There's also a little segment of hose on the pump that can fracture. When this happens, the pump works overtime to keep pressure and when you fuel level reaches 1/2 or less, the may suck air making matters worse.

Or someone just doesn't like you and topped off you tank with Miracle Grow.