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Thread: Rich At Idle

  1. #1

    Default Rich At Idle

    I purchased an Airstream Motorhome with a 454/turbo 400 and the Holley Commander 950/Innovate wideband O2 sensor installed. The engine runs great at idle, cruising speed and under load, except the A/F ratio at idle is between 11-12. Above ~1600 RPM and at cruising speed, the AFR is ~14.3, when decelerating, it briefly jumps up to 17-18 and then right back down 11-12.

    It has the stock manifolds with some leaks down the line where sections are clamped. I am planning on installing a Banks system this spring.
    Could the exhaust leaks be causing the low AFR at idle? What else should I be looking for to correct this very rich idle issue? Thanks.
    Last edited by PeterH; 01-07-2016 at 09:13 PM.

  2. #2
    Join Date
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    Quote Originally Posted by PeterH View Post
    Could the exhaust leaks be causing the low AFR at idle?
    Ensure there are no exhaust leaks upstream of the wideband O2 sensor(s) to prevent a false lean condition.
    The WBO2 sensor's false lean condition will inform the ECU to enrich the fuel to a point where it's excessively rich.
    Ensure sufficient length of exhaust piping beyond WBO2 sensor(s) to prevent a false lean condition at idle & low RPM.


    What else should I be looking for to correct this very rich idle issue?
    The Commander 950 Fuel Map needs to be tuned. It's not a self-tuning EFI system.
    http://www.chevytalk.org/fusionbb/sh...?post/2236964/ (C950 Fuel Map Tuning Procedure)
    http://forums.holley.com/showthread....2773#post12773 (Additional Fuel Map Tuning Tip)
    http://forums.holley.com/showthread....6662#post26662 (Ignition Timing Synchronization)
    http://forums.holley.com/showthread....e-Tuning-Notes (EFI Idle Tuning Notes)
    https://www.holley.com/document/tech...y_r10149-7.pdf (Commander 950 Manual)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

    Default

    Thank you very much for the info and all the links. After spending several days fine tuning everything, it's running very good. I still have a little "surging" at idle, but the AFR is good at idle and under load and various speeds. I kept the WBO2 Compensation Limits at 20%, is that OK or should I lower them for daily use?

  4. #4
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    Quote Originally Posted by PeterH View Post
    I kept the WBO2 Compensation Limits at 20%, is that OK or should I lower them for daily use?
    That's fine. When I used the Commander 950, I kept the WBO2 Compensation Limits at 25%, except in the WOT cells.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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