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Fix It Man
Fix It Man, Master Technician
Category: Ford
Satisfied Customers: 17368
Experience:  ASE Master Certified, AA Degree Auto/Diesel
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2004 Ford -150 STX - 4.6 litre V8 Symptom: The truck will

Customer Question

2004 Ford -150 STX - 4.6 litre V8
The truck will not accelerate well at all, and shift erratically under acceleration. Can drive very slowly, but no power to accelerate, or pull up hills.
Current codes P0102 low signal from MAF, and P2106, Throttle Position Sensor, Forced Limited Power.
The MAF has been replaced, but the problem remains. I’m looking at the TPS or Throttle Body at this point, but would like some Ford F-150 specific advice?
Submitted: 1 year ago.
Category: Ford
Expert:  Fix It Man replied 1 year ago.

Hello, my name is Bobby. Thank you for the question. Can you tell me how many miles are on the truck. Are these same codes still coming back after the air flow meter was replaced?

Customer: replied 1 year ago.
The truck has 165000 miles on it, and yes, the codes will come back after the MAF was replaced. When you first start the truck, it will idle fine. Once you put it in drive, and start moving forward (pulling out of the driveway, as an example) the "wrench" light will come on, and it will stumble. You can tell when it goes into Forced Power Reduction mode.
Customer: replied 1 year ago.
I should have said "Forced Limited Power" mode..... can't keep that term in my head :)
Expert:  Fix It Man replied 1 year ago.

Thank you. So I know where to proceed can you tell me if you have a fuel pressure tester and if your scan tool reads live engine data?

Customer: replied 1 year ago.
No fuel pressure tester, and no, scanner does not read live data.
Expert:  Fix It Man replied 1 year ago.

These would really help in diagnosing this and not just throwing parts at it. It may be the TPS but low fuel pressure can cause these also.

Customer: replied 1 year ago.
you're thinking it may be a clogged fuel filter? If I had such tools, what would I do and what would I look for?
Expert:  Fix It Man replied 1 year ago.

You would install the pressure gauge to the test valve on the fuel injection rail. You should get about 35-40 psi. You could start with the filter if that has not been done recently.

Customer: replied 1 year ago.
What would I look for with a scanner that can view live data?
Customer: replied 1 year ago.
The same, would tell me what the fuel pressure is?
Expert:  Fix It Man replied 1 year ago.

The scanner won't tell you what the fuel pressure is. You need to look at the fuel trim readings. They are STFT and LTFT. If they are more than about 8 constantly then the engine may not be getting enough fuel.

Customer: replied 1 year ago.
Thanks, ***** ***** fuel pressure is low, check filter, fuel lines for clogs, etc? If pressure is good, what would be the next step?
Expert:  Fix It Man replied 1 year ago.

If fuel oressure is low replace the filter. If it continues replace the pump. If the pressure is fine then see what the TPS sensor reading is with the scan tool and see if the signal moves smoothly without interruption when pressing the pedal