Vehicle Losing Power When Accelerating

[BOB4254]

My issue, will accelerate to 2000 RPM. Then when I floor it engine bog's down. When I let up on the gas pedal half way, engine accelerates and takes off as long as I keep her around 2000 RPM. No miss firers. New plugs, coils and wires. New fuel pump. Cleaned MAF. Getting Codes P0171 & P0174. 1998 Ford Expedition 5.4L, 130k miles.

 

[Billme]

Did you change the fuel filter, check fuel pressure at rail?

 

[BOB4254]

Fuel filter changed 20k miles ago. Pressure at rail = 29

Feels like she's not getting the fuel she requires when accelerating bogs down.

Could it be a bad Fuel Pressure Regulator???

Very smooth and quiet idle.

 

[Billme]

It sure could, that would be my next move..

 

[BOB4254]

Installed new Fuel Pressure Regulator. Condition did not improve.

Something very interesting someone may have an answer to. I installed a new fuel filter. OMG she accelerated like she did when she was new. I thought my acceleration problem was solved. Next day I started her she started fine and idles smooth and quiet.

Took her for a spin and now she when back to very poor acceleration. Same problem I had.

(will accelerate to 2000 RPM. Then when I floor it engine bog's down. When I let up on the gas pedal half way, engine accelerates and takes off as long as I keep her around 2000 RPM).

I'm thinking to install new MAF Sensor.

Any advice. Very confused at this point.

 

[Billme]

From what I have read, the EGR valve can compromise acceleration pretty dramatically..

 

[BOB4254]

Thanks for your post Billme. I'll check the EGR valve. I have had to replace once before. 50,000 miles ago.

Let you know the result.

 

[99WhiteC5Coupe]

Installed new Fuel Pressure Regulator. Condition did not improve.

Something very interesting someone may have an answer to. I installed a new fuel filter. OMG she accelerated like she did when she was new. I thought my acceleration problem was solved. Next day I started her she started fine and idles smooth and quiet.

Took her for a spin and now she when back to very poor acceleration. Same problem I had.

(will accelerate to 2000 RPM. Then when I floor it engine bog's down. When I let up on the gas pedal half way, engine accelerates and takes off as long as I keep her around 2000 RPM).

I'm thinking to install new MAF Sensor.

Any advice. Very confused at this point.

If you replaced the fuel filter and it ran fine for a short period of time - then began the bogging / fuel starvation issue, I’d bet you got a tank of bad gas with some type of contaminant (or someone put something in your fuel tank).

The new fuel filter probably loaded-up with whatever was in the fuel tank - and now you’re having the same problem.

Do you have the old filter? If so, cut it in half and see if the filter media is loaded-up with debris.

 

[BOB4254]

Yes I thought the same thing. I will cut old filter open.

I have locking gas cap so gas tank cannot be accessed to put something in tank.

Before installing new fuel filter I checked gas in tank for contaminants. 8 glass jars, clear fuel.

I have always used Shell gas and Shell/Nitro for last 2 years.

Thanks for your post and advice.

 

[Billme]

The above could be..but
Unfortunately we get the same symptoms for different problems.. For this reason, I try to do the easy stuff first..
The throttle position sensor can do your symptom too
This is a good video to watch

Symptoms of a Bad Throttle Position Sensor and How See if it Has Failed

Symptoms and signs of a bad throttle position sensor (TPS), how it works, and how to see if it has failed. Read here for more information. https://www.backya...

youtu.be