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P0171 Trouble Code on 2000 Lexus ES 300 with 1MZFE Engine - Power Loss and Hesitation During Acceleration

Model: 2000 ES 300 Fault Code: P0171 Posted: 2011-04-26 16:23

Hi everyone! I'm new to this forum and have found it extremely helpful. I'm currently facing a serious issue after installing a 1MZFE engine into my 2000 Lexus ES 300. The vehicle now shows a P0171 trouble code, which is causing significant performance problems. During wide-open throttle acceleration, there's a severe loss of power—almost as if the engine doesn't rev properly and exhibits heavy hesitation. I suspect limp mode may be active. I've already checked all vacuum lines, intake and exhaust systems, replaced the air flow sensor (AF Sensor), and cleaned the MAF sensor—everything I could think of has been done. Despite these efforts, the issue persists. Has anyone else experienced this exact problem when swapping engines in a 2000 ES 300? Any insights or troubleshooting steps would be greatly appreciated.

Related fault codes
P0171
Comments (3)
Anonymous 2011-04-26 16:53

This is not a Mercedes vehicle—correct model is Lexus ES 300 with 1MZFE engine.

Anonymous 2011-04-27 06:47

Confirmed: This is a 2000 Lexus ES 300 equipped with the 1MZFE engine. The P0171 code and performance issues are common in this setup after engine swaps.

Anonymous 2011-08-10 20:24

Have you recently checked or replaced the fuel filter? A clogged fuel filter can cause lean conditions, which may trigger the P0171 code and result in poor acceleration and hesitation.