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Thread: 550-400 TBI stalling when stopping, and I need a replacement part.

  1. #1
    Join Date
    Jul 2016
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    Colorado Springs, CO
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    Default 550-400 TBI stalling when stopping, and I need a replacement part.

    After years of stalled progress, I'm finally getting my project vehicle going. So far it's mostly going well, but I'm having a problem. It starts & runs mostly just fine. The problem arises when I'm coming up to a stop. If I gradually brake and roll up to the stop, everything works fine. But if I brake hard, it has a tendency to stall.

    It's a mild AMC 401 V8 with an RV cam connected to a 700R4 transmission. I have the lockup torque converter working as it would in a factory GM car, with the vacuum switch and brake switch in place. So the lockup torque converter is unlocking properly. It's set to an idle speed of around 600 RPM and it will occasionally drop below that. Sometimes it catches itself and surges a little (which can be disconcerting when you don't expect it). But sometimes it will stall out. It restarts just fine. Part of the problem is that the handheld controller is basically dead. The LCD screen is shot and it doesn't appear to be working at all. So I can't monitor the system or change any settings. Is there any way to get just the replacement handheld or do I need to just eat the cost of getting a computer & handheld (554-116)?

  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    All you need is the new 3.5" LCD Touchscreen unit (LINK).
    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
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    Quote Originally Posted by Danny Cabral View Post
    All you need is the new 3.5" LCD Touchscreen unit (LINK).
    I ordered the touchscreen and it showed up today. Got the firmware pushed back to the version that will talk with my ECU (0.4x) and I was able to poke around and see all the settings. But I'm trying to figure out what setting(s) I need to adjust to deal with my stalling issue. Do you have any suggestions of what to try?
    My first effort will be to just simply turn the idle speed up. It's set at 750, but I'm going to try notching it up a little to see what effect that has on the system as a whole.
    EDIT: Would I benefit from an ECU firmware upgrade? If so, which ones would be compatible with my ECU/TBI setup?
    Last edited by grimmjeeper; 09-16-2017 at 04:38 PM.

  4. #4
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    Quote Originally Posted by grimmjeeper View Post
    But I'm trying to figure out what setting(s) I need to adjust to deal with my stalling issue. Do you have any suggestions of what to try?
    In the Holley EFI software (LINK), look at where the live cursor moves to on the Base Fuel & Timing Tables.
    Determine if it's stalling due to a lean or rich condition, and manually tune this area of the Base Fuel Table.

    EDIT: Would I benefit from an ECU firmware upgrade? If so, which ones would be compatible with my ECU/TBI setup?
    First inform us of which EFI software/ECU firmware version you're using:
    http://forums.holley.com/showthread....5760#post45760 (Determining EFI Software/ECU Firmware Versions)
    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
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    Nov 2014
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    Ont. Canada
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    Have you properly set the throttle shafts? If the throttle shafts are closed too much and it's using too much IAC to hold your Target Idle Speed, it can act up like you are describing. I shoot for a IAC Position of between 0%-10% at idle.

  6. #6
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    Jul 2016
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    Quote Originally Posted by Danny Cabral View Post
    In the Holley EFI software (LINK), look at where the live cursor moves to on the Base Fuel & Timing Tables.
    Determine if it's stalling due to a lean or rich condition, and manually tune this area of the Base Fuel Table.
    I haven't had a chance yet to test it on the road. I'll do that when I can.

    Quote Originally Posted by Danny Cabral View Post
    First inform us of which EFI software/ECU firmware version you're using:
    http://forums.holley.com/showthread....5760#post45760 (Determining EFI Software/ECU Firmware Versions)
    ECU firmware:
    Serial number (I can send it if you need it.)
    Date Code 20111222
    Version 0.0.397
    Profile #1

    Controller firmware:
    Device type 10
    Device firmware 0.0.46
    The ECU is untouched (as far as new S/W) since I bought it 5 or so years ago. The controller had the 0.0.46 available from the factory and I changed it from the default 4.x that it was set up with.

    Quote Originally Posted by 81 TransAm View Post
    Have you properly set the throttle shafts? If the throttle shafts are closed too much and it's using too much IAC to hold your Target Idle Speed, it can act up like you are describing. I shoot for a IAC Position of between 0%-10% at idle.
    That I haven't done. I went & checked it. At the default of 750 RPM, it was at 35%. I set it up to 850 RPM and it was at 42%. So I guess adjusting the throttle is in order before I do anything else. I did notice that the engine runs smoother when set at 850 RPM.

    For reference here's the engine specs:
    AMC 401 ci V8 bored over .030".
    Stock heads, valves & exhaust.
    Comp Cams 10-201-4: 212°/212° @ .050" duration with .477"/.477" lift at the valve. Stock stamped rocker arms.

  7. #7
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    I got the throttle adjusted to hold 1% IAC. Dialed it up until RPM started rising and then backed it off just enough to come back to 750 comfortably. But I have a dinner engagement, so no test driving until tomorrow.

  8. #8
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    Nov 2014
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    Don't forget to do another TPS Autoset.

  9. #9
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    So I was able to take a spin around the block. Did the TPS Autoset before I left. Also checked and I was set to a 14.0 A/F mixture. Bumped it up to 14.7. But also the IAC jumped back up to 30% so I'll have to chase that down.

    It didn't stall like it had been. But the A/F mixture did drop lean when I was braking/slowing down. Into the 12s and even 11s. But it's getting late and it's dark out, so I'm going to hang it up for the night. I'll tweak some things tomorrow. But it's definitely getting better. Thanks for all the help.

  10. #10
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    Quote Originally Posted by grimmjeeper View Post
    ECU firmware: Version 0.0.397
    That's V1 ECU firmware. You need to update your EFI software/ECU firmware versions (LINK). There have been many EFI functionality updates/improvements since then.
    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

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