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Thread: C950 Off Idle Stumble

  1. 03-09-2020, 10:26 AM #1
    resto-mod
    resto-mod is offline Junior Member
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    Default C950 Off Idle Stumble

    I've gotten past the initial setup and the engine starts and cruises great. I have three (hopefully) minor issues in the programming area that I'm hoping someone can help me with. TIA to all of you Commander 950 gurus!

    1) I have a bit a lag/stumble when going from idle to mild acceleration.

    2) When the engine is warm, it seems to need approximately 4-5 seconds of turning over before it finally starts.

    3) When the engine is cold, I'd like to have it go to 1200-1500 RPM, but right now it's about 850-900 and the idle is a bit rough until it warms up.
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  2. 03-09-2020, 10:36 AM #2
    Danny Cabral's Avatar
    Danny Cabral
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    Quote Originally Posted by resto-mod View Post
    1) I have a bit a lag/stumble when going from idle to mild acceleration.
    Pulse Width - Rate of Change of TPS (TPS based Acceleration Enrichment).

    2) When the engine is warm, it seems to need approximately 4-5 seconds of turning over before it finally starts.
    Try decreasing the Cranking Pulse Width (msec of fuel).

    3) When the engine is cold, I'd like to have it go to 1200-1500 RPM, but right now it's about 850-900 and the idle is a bit rough until it warms up.
    Increase the Desired Idle RPM at that temperature range.
    May God's grace bless you in the Lord Jesus Christ.
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  3. 03-09-2020, 05:21 PM #3
    resto-mod
    resto-mod is offline Junior Member
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    Thanks for the quick reply Danny! You are an awesome resource for these adjustments! As you can probably tell by my questions, I'm neither a computer or EFI genius.

    1) What amount of (% or number amount) of enrichment do I add or subtract from the original number? Example: "Subtract 3% to start with, then add 1-2% until the stumble goes away."

    2) What would be a good (noticeable) number of milliseconds to decrease it by Example: 1, 5, 20? For a GM 383 SBC where should it be now?

    3) I think I can handle this one. I just type in the desired RPM value for the engine temperature value?
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  4. 03-17-2020, 05:05 AM #4
    Bill C
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    If you do not have the manual Holley supplies with the C950, please download it and read it several times to become intimately familiar with it. It has a very good from start to finish tuning process that even the most inexperienced users can understand, follow, and get good results. I'd encourage you to read it.
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