Codes P0171 and P0174

1997 FORD THUNDERBIRD
275,000 MILES • 4.6L • V8 • RWD • AUTOMATIC
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TERESA BISHOP
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So we have these codes. We replaced 02 sensors, MAF sensor, used cataclean. Checked EGR and valve. Checked for vacuum leaks. Car runs worse with everything we try. Ready to junk it. What else can it be? If our fuel pressure gauge is working it has 9 psi. It has weak start. When you punch the gas it bogs down. After replacing MAF it quit running three times driving down the road.
Sep 28, 2017 at 9:35 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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STEVE W.
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If the fuel pressure gauge is correct your fuel pump is toast. You should have at least 38 psi. Normally you should have 38-45 with the key on engine off.
Sep 28, 2017 at 11:38 AM
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TERESA BISHOP
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It is a new cheap pump got off eBay. Got the MAF and 02 sensors off eBay too.
Sep 28, 2017 at 11:49 AM
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STEVE W.
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if it is showing 9 PSI it is not going to run very well if at all and you will get other codes because it is running very lean.
Try RockAuto.com. or your local parts store.
Sep 28, 2017 at 12:17 PM
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TERESA BISHOP
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So now after I drove it a while today I am getting a code for throttle position sensor. Are you saying we're getting false codes?
Sep 28, 2017 at 3:29 PM
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STRAILER
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Yes, it sounds like you need to replace the fuel pump.

Here is a guide and some diagrams to help you get the job done:

You will need to raise the car up safely to begin.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

and this guide will give you an idea of what you are in for when doing the job.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Diagram (below)

Please let us know what happens and upload pictures or videos of the problem.

Cheers, Ken
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Sep 29, 2017 at 10:11 AM