Thanks,probably test this week.Can i test pressure at WOT while not moving or do i have to be driving?

 

It would be better to be moving, unless you can power-brake it and not spin the tires

 

Did fuel pressure test.30 psi at idle,raises slightly with rpms,disconected regulator pressure went to 40,reconnected & shut truck off,pressure went up to 37psi in 10 minutes.Does this sound right?Dealer said pressure should be in 40 range.

 

Asked dealer again about pressure they said book lists 30 & 45.Pretty vague.Anyone test their pressure?Looking for a second opinion.30 sounds a little low.

 

You've gotta do the pressure test while the truck is having the problem

For what you did, those pressures sound right. It should be 28-30 at idle, 40 with the engine off and key on (or by disconnecting the vacuum to the regulator when running).

You really have to check the pressure when the truck is ******* down.

 

Sounds like me plowing snow on a two track for 14 miles... sucked the air cleaner full of that fine powdery snow that is curlin' up behind the blade. As I let off the throttle at the top of the hill, (again... 19 miles out, 14 on a two track) the truck falls away and dies. OH no...

Seriously... sounds like you have checked everything. Air coming in OK, exhaust getting out OK, Fuel pressure is my first guess.

This plow truck acted like yours when the fuel pump was on it's way out. Would plow @ low rpms and low power demand OK, but... hit the road and ask for more power and it just died away like you were in the mud.

I had a service guy tell me about a wire in (I think) the MAF sensor that was in the wrong spot. I thought at the time it was a con-job BS thing. Like I am an ignorant consumer. I mean come on... the truck had 120k on it and it ran just fine with this wire in the wrong spot in the harness/plug until I brought it to you and now it needs to be fixed??!!??
The long story is...I was desperate for a bar-type torque wrench to measure rotating torque on the pinion for a re-bearing job on the rear-end in this plow truck. Has to be in service tommorow. I live in the boonies. A local mechanic borrowed me this tool. Mechanics NEVER borrow you their tools. So to say "thank-you" I took my truck to him when my fuel pump was going bad. Rust free TX truck - nice to work on. Charged me 680.00 to change my fuel pump. Checked exh backpressure, MAF, FP-reg, etc, etc, and didn't even kiss me or pinch my nipples while he was scr#%&ing me. I hate that.

 

I re-read and you said you cleaned the MAF sensor. That is a very delicate, sensitive instrument. Is there a way to check it's operation?
How about a TPS throttle position sensor?

 

if the MAF sensor is bad cleaning it does nothing. it sounds like a bad MAF. unplug it and then drive it. the computer will go to a base setting and should drive better.

 

Did you look in the throttle body? Maybe the plate is sticking?

 

Did try disconnecting MAF.It made the trans. slam into gear so i couldnt drive it hard.Cleaned throttle body.Checked TPS for voltage per Ford Fuel Injection testing procedure.Got to get longer fuel line to test driving fuel pressure.

 

Road tested.27-28 psi coasting(foot off pedal)driving normal mid 30s wide open 37 to38 psi.

 

Sounds about right.

 

Has anyone tested your knock sensor? It might be bad and retarding your timing.....excuse me..........developmentally disabling your timing.

Also, I had a (non-Ford) engine behave like this. Mine felt great until I would hit about 3200 RPM, then it would rev no higher, it had no more power and vibrated. Turned out to be my timing chain had jumped a tooth and was about to cease becoming a timing chain and evolve into scrap metal.

 

I had thought of checking that.Dont know exact location or how to test?(Ford Fuel Injection )has a lot of testing procedures if anyone needs info.Nothing for knock sensor in 5.4. P.S. Im about tested out.

 

Can knock sensor be unpluged to test.Cant find a test for this.