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Thread: Sniper Stalling After Coasting

  1. #1

    Default Sniper Stalling After Coasting

    OK, so I've been trying to sort this issue out for a little while, and have tried almost everything I can think of.
    Sniper has been on my 350 small block for about two weeks now, and I'm very happy with it, only have this one issue.

    Car has manual transmission, and when coasting up to a light in gear, it drops a heap of revs and nearly stalls once I push the clutch in to stop.
    Tried playing around with the IAC settings, different Decay Rates and Hold Positions etc., hasn't made much difference.
    Even tried adding fuel into the Base Fuel Table in those areas to prevent the lean condition, but hasn't helped either.
    (Idea was to try & help the Learning process due to the small amounts of time it was in those areas to Learn, and just how lean they were getting.)
    Hot idle is 800 and 4-5% IAC Position, back to standard 30% Hold, 1000 RPM Above Idle Ramp & 4 second decay. It doesn't seem to be "Learning" the problem away, and not too sure what to do next.
    Currently fuel only, but want to setup timing control this weekend (maybe that would prevent the idle overshoot?). I'm reluctant to do it until I know that everything is good with the fuel control though.
    Advance is 15° at idle & 36° total.

    Screenshot attached of datalog showing a good example of what happens. Anyone got any suggestions? Have datalogs, so if you want any other info just ask and I can find it. Have tried nearly everything I can think of before asking for help.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    Quote Originally Posted by 91chevota View Post
    Hot idle is 800 and 4-5% IAC Position, back to standard 30% Hold, 1000 RPM Above Idle Ramp & 4 second decay.
    It seems your throttle blades are open far enough, and you've maximized the IAC parameters to prevent this.

    (Idea was to try & help the Learning process due to the small amounts of time it was in those areas to Learn, and just how lean they were getting.)
    Even tried adding fuel into the Base Fuel Table in those areas to prevent the lean condition, but hasn't helped either. It doesn't seem to be "Learning" the problem away, and not too sure what to do next.
    I suspect the Base Fuel Table is still too lean in that deceleration/return to idle area of the Base Fuel Table.

    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    I find the most helpful datalog function, is overlaying the datalog on your Global File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Global Folder screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Global Folder (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    http://forums.holley.com/showthread....s-amp-Datalogs (Datalog & System Log Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    http://forums.holley.com/showthread....7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

    Default

    Quote Originally Posted by Danny Cabral View Post
    It seems your throttle blades are open far enough, and you've maximized the IAC parameters to prevent this.
    I ended up back at these settings after trying different combos of them to see if it would help the problem. Changing those parameters didn't seem to help, so I went back to the standard settings to keep a bit of a baseline for other things I tried changing.

    Quote Originally Posted by Danny Cabral View Post
    I suspect the Base Fuel Table is still too lean in that deceleration/return to idle area of the Base Fuel Table.
    Thanks Danny, I'll have a read through that info when I have a chance.
    When I was searching the problem, I saw a few posts (including yourself in another section of Holley forums) that suggested this problem can be caused by a lean condition at or around idle.

    The overlays were where I started manually tuning the fuel table in & around the cells that it crossed through during the stalling problem. I was fairly conservative with how much fuel I put in those areas (about 5%), but maybe I should try putting in a fair bit more? AFRs approach 20 during the stall events, so it is running very lean. I think this could be partially to do with the fact that once it drops below 500, it reverts back to Cranking Fuel?

    Only other thought I had was that once it drops below idle, the IAC opens a long way to try and bring the idle back up (between 25% & 30% depending on how low the RPM gets). Is it possible that the large IAC Position at low RPM could cause the lean condition? Or is the real problem the lean condition and the IAC opening is simply a symptom? My understanding is that the ECU should be injecting the right fuel based on RPM & MAP, regardless of IAC \Position? Just a thought.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,669

    Default

    Quote Originally Posted by 91chevota View Post
    The overlays were where I started manually tuning the fuel table in & around the cells that it crossed through during the stalling problem. I was fairly conservative with how much fuel I put in those areas (about 5%), but maybe I should try putting in a fair bit more? AFRs approach 20 during the stall events, so it is running very lean.
    If it's happening due to a lean condition, I'd add more than 5% in that area of the Base Fuel Table.

    I think this could be partially to do with the fact that once it drops below 500, it reverts back to Cranking Fuel?
    To avoid this issue, the Crank To Run RPM parameter is usually set to 400 RPM in all Holley EFI systems.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    Ever find a solution to the problem?

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