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I have a 2001 Toyota Corolla.

Lately it has been throwing the P0171 code (system too lean). My short term fuel trim is normal at idle. +/- 5 % at idle and long term fuel trim is high at idle +18 %.

When I rev the engine to 1500 rpm the short term stays the same and long term fuel trim goes down to about 14%. Weird thing is when I drive the car, the short term fuel trim is normal and the long term goes down to 7 percent or so, BUT intermittently at around 2200 to 2500 rpm the short term shoots up to around 25 percent and long term fuel trim goes to 35 %. This is the point where I throw the P0171 code.

Any help would be appreciated.

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  • Welcome to Motor Vehicle Maintenance & Repair!
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Oct 23, 2018 at 0:40
  • I'm not sure, but I'd start with vacuum leaks - especially inspect the intake hose(s) and look for cracks. This could be a "false air" or "unmetered air" issue.
    – SteveRacer
    Oct 23, 2018 at 7:24
  • Jake, are you accelerating when the STFT spikes?
    – Zaid
    Oct 23, 2018 at 7:28
  • Thank you, SteveRacer, this is what i was thinking also. And Zaid, yes i believe i was accelerating when the stft spikes. I would have to check. It only does this once every few miles though. And the engine load was 35 percent when my computer threw the code
    – jakester89741
    Oct 23, 2018 at 17:45

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