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Sounds like a vacuum leak when put in park on my E-Street EFI

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  • Sounds like a vacuum leak when put in park on my E-Street EFI

    This has been an ongoing problem for months the car run great in drive but when I get to the destination I put it in park AFR correct goes up and down. The O2 sensor been replaced, I rebooted the EFI then after driving around it does it all over. Edelbrock tech state to try shaking the harness and check for exhaust leaks. Done all that. Is there another sensor I should be checking?

  • #2
    We need some more information to help you figure out what is causing the fluctuation. What is your base ignition timing? Do you have vacuum advance? Which port is it hooked to on the throttle body? What is your base idle speed with the IAC hole plugged? What is your idle AFR setting? What is the AFR Correction at idle? What is TPS reading at idle?

    With that information, we can move forward.

    Comment


    • #3
      Hey Steve

      No changes have been made on tablet after erasing and running wizard setup for a stock GM crate engine a couple days ago.
      Here the reading before I drove the car
      Temp 156
      What is your base ignition timing? 16#
      Do you have vacuum advance? Yes, Hose is good
      Which port is it hooked to on the throttle body? Top Right (Pass)
      What is your base idle speed with the IAC hole plugged? RPM 756 unplug and plugged
      What is your idle AFR setting? 13.4
      What is the AFR Correction at idle? 7.65
      What is TPS reading at idle? 10

      After driving
      Temp 172
      RPM 795 to 843
      Vac 19.0 to 20.4
      AFR 12.90 to 13.54
      AFR Correct -5 to -10

      Thanks for the help

      Doug


      Comment


      • #4
        OK so it looks like you have a stock cam and your readings look good. Our systems run closed loop fuel mixture correction all the time, so the AFR will never lock onto one number like the TPS does at idle. Some variation is normal, if it is moving around, but the idle RPM is pretty steady, then the system is operating normally. You didn't mention if you had an unsteady or surging idle.

        I would suggest bumping your ignition timing to 18 degrees base timing and lean your target AFR to 13.9-14.0. This will help overall and help mileage somewhat. Of course you will want to listen for pinging or detonation and if you hear any, then back it down to 16 degrees.

        Watch your AFR correction and as long as it stays below 10% on average, you are good to go. If it is more than that, then we may need to change the map you are on.

        Comment


        • #5
          You didn't mention if you had an unsteady or surging idle.

          RPM 795 to 843 That's unsteady or surging there abnormal.
          Vac 19.0 to 20.4
          AFR 12.90 to 13.54
          AFR Correct -5 to -10

          Comment


          • #6
            795 to 843 is less than 50 RPM. That is totally normal for an E-Street system. If it is above 100 RPM, then that is unsteady. Factory tachometers have some damping built into them so that the needle stays steady, but the actual engine RPM is moving 50-100 RPM, you can see it on the tablet without damping, but the factory tach will be steady.

            On Pro Flo 4 with ignition timing control, you will see the idle speed variation be under 50 RPM, but not by a whole bunch.

            When you shift from Drive to Park you are changing the load on the engine and it takes a second to adjust to the load change. If you drive it, then shift into Park, how long to you see a variation? Your original post stated the AFR was changing, not RPM.

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