Car lacks power, p0171 and knock sensor codes

1999 LEXUS ES 300
160,000 MILES • AUTOMATIC
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WALLY AB
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  • 97 POSTS
Car won't rev past 3,000 or 4,000 RPM's, hesitates to pick up speed past 1/2 throttle.

Seller said it was an oxygen sensor but I also bought fuel filter in case it might be a fuel problem.

Is there anywhere I can start from to test it?
Feb 24, 2020 at 7:28 AM
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KASEKENNY
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Okay. I attached the testing for this. Basically it could be an o2 sensor but there are other causes. The only way to know for sure and not guess is to run through the test.

Let me know what questions you have as you work through it. Sorry there is no easy button but we just need to run through it.
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Feb 24, 2020 at 2:07 PM
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JIS001
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Check the air boot between the air box and throttle body. If the boot is torn it will post lean code P0171 and hesitation problems. As the vehicle ages the air boot gets very hard and brittle. When replacing the air filter it splits open. Let us know how that air boot looks please.
Feb 29, 2020 at 12:48 AM
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