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  • #1

    New Build - O2 sensor out of range

    New build - 400Hp SBC in '76 vette, 350cid with mid cam profile. brand new Pro-Flo4. = all sensors are OK but O2 sensor out of range. I can not get O2 sensor to be in range (green). AFR is high at 22+. can not change. fuel is pouring thruthe engine. Could not get IAC less than 80% during set up regardless of idle speed. set idle at 725 rpm and moved on. Car is set at 12 degrees BTC but running extremely rough due to the massive amount of fuel being injected. 29# injectors at 58psi (edelbrock sump EFi pump)
    disconnect O2 sensor and diagnostic light goes from red to green (that I don't understand.) AFR drops.
    any idea why O2 is not in range?
    Thanks, Joe
    Last edited by joe emaus; 08-04-2020, 07:07 PM.
    Tags: None
  • #2
    It sure sounds like a bad O2 sensor to me. The O2 sensor is saying your mixture is lean and the ECU is injecting additional fuel. Test your O2 sensor. Are you running the XT or 4150? I have a PF4 4150 on my 71 454 Vette. So far I am happy with the results but I really haven't had a chance to run it on the street yet. It is currently getting body work and paint done.

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    • #3
      bad O2 was my thought as well but it is new. Position on the exhaust would not cause the problem I assume as it is close to Edelbrock recommendation. I research how to check the sensor.. Thanks.

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      • #4
        Here you go. https://www.youtube.com/watch?v=Xsr55FInfwk

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        • #5
          Do you have exhaust system on car? If not that can cause high AFR reading.

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          • #6
            yes, exhaust on. car is complete. Can run car after loading mid performance MAP and turning off learn function immediately although IAC is 80%. Turn on learn and tune goes ultra rich.

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            • #7
              If you screw in on the idle adjusting screw the IAC will not come down any at all?

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              • #8
                No. O2 sensor tested bad. No response at all. AFR constant 22.8.
                Edelbrock sending new sensor. Will start over.
                Thanks for the replys.
                Joe

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                • #9
                  I just ran into the same thing, PF4 kit sat on the shelf before using for quite some time, likely not warranteed.

                  Did the new O2 sensor fix it? Going to try to run test today and see if sensor is bad.

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                  • #10
                    Originally posted by My427stang View Post
                    I just ran into the same thing, PF4 kit sat on the shelf before using for quite some time, likely not warranteed.

                    Did the new O2 sensor fix it? Going to try to run test today and see if sensor is bad.
                    https://www.summitracing.com/parts/bch-17025


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