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Thread: LE5 Idle Spark Control Issues

  1. #1
    Potential Tuner
    Join Date
    Apr 2021
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    LE5 Idle Spark Control Issues

    Long time lurker, first time poster. I am working an LE5 2.4 project and it is my first time tuning with HP Tuners.

    The engine is a 2.4L LE5 out of an 07' HHR. Running a manual trans from a Solstice/ Sky. Engine is completely stock. Exhaust is only about 1.5-2' past the manifold and air intake is using stock HHR throttle body elbow, connected to a 6" straight section with the stock card MAF, and a generic cone filter on the end. Running 60psi of fuel pressure. Pressure is constant.

    When idling, the idle spark jumps from about -5? to 30?. When I turn off idle spark control in VCM scanner and leave it locked at 5? it idles nicely. Setting it to -5? I get the best vacuum reading playing around with it.

    I attached my tune and log file.

    What confuses me as well is the engine vacuum slowly decays from about 20-22inHg to 14inHg. I checked this with a manual gauge and got the same thing. Sprayed all around the intake with intake cleaner and no increase in RPM so I don't believe I have a vacuum leak. Note the vapor purge sensor has been removed from the vehicle/ tune and is capped off at the intake manifold port.

    I will also get 2 codes that pop up, P0171 for system too lean and P0300 for random misfire. My thought was that this may be caused by the erratic idle spark and not necessarily what is contributing to the idle spark. Unfortunately my wideband isn't hooked up yet.

    I've been poking around looking at the Idle Adaptive Spark Control. Any input on where to begin would be appreciated.

    HHR Tune 4-3-21 2.hpt
    Start 8 4-3-21.hpl

    Thanks

  2. #2
    Potential Tuner
    Join Date
    Apr 2021
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    2
    For anyone curious about a fix that has the same problem, I was able to solve the issue.

    The erratic idle was actually being caused by the cooling fan. Yes, the cooling fan. When the fan is on the air filter was getting a good enough draft to affect the MAF. When shielding the filter the problem went away and the idle spark settled down.

    The STFT was maxxed out and I was still showing lean on my WBO2. There was a small vacuum leak at the brake booster that was pulling fresh air in. I may still replace the intake gasket as I can affect the O2 reading by spraying carb cleaner at the intake where it meets the block. The O2 readings are cycling as they should and I am at 14.7 now on the WBO2 at idle.