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Thread: AMC 360 - Strange stumble after throtle blip.

  1. #1

    Default AMC 360 - Strange stumble after throtle blip.

    Total noob question so please forgive any stupid questions! I have a AMC 360 with a Edelbrock Performer Plus (Idle-5500) cam, Edelbrock Performer Intake, 57.92 cc heads & Wiseco .045" oversize flat top pistons. It's a fresh rebuild and has previously had a Holley Street Avenger carb installed. I've changed to the Sniper EFI and it idles great. I have followed the instructions as far as I can tell to the letter, and set the idle screw & idle speed with the IAC hole taped to a RPM of 740 all at a running temp of 185°F. It Idles smoothly at about 790/800 with a AFR of 13.7 and the IAC reading 2-3%.

    It revs & sounds really strong, I have test driven it for a couple of miles and really pleased with the overall performance apart from a strange stumble after a throttle blip. Back on the driveway, if I rev the engine up to 2500 and then let go, the revs drop and almost stall (sometimes it does stall). At the point of the low revs, the AFR shoots up to the high 20s. If it does not stall it eventually recovers with a stumble and an AFR between 10-12 before returning to the normal idle.

    I have tried playing with the IAC ramp and fuel tables, but I'm not really getting anywhere. I have reverted back to the base calibration (368ci, mild cam) and the problem persists. Any help would be appreciated.

  2. #2

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    If I understood correctly, the stumble happens when returning to idle after revving her in neutral (and sometimes also in gear, when giving a short burst of throttle, say, to hop up a curb while parking)? My engine did that too. It got much better after a few days of letting the ECU Learn and then moving the Learn Table to main.

    Also, record a datalog file and check how rich she goes from Acceleration Enrichment (AE). If she goes too rich, lean out the AE table (if you click on the corresponding point of time in the log window, the currently active AE parameter will be highlighted in the config window). That might help as well as the Sniper might over-correct the rich spike from too much AE into a lean spike.

  3. #3

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    Hi Dr_grip. Yes it happens after revving in neutral. I'll take a look at the datalog. I have let it Learn an bit and transferred the settings. When I do this, I see a big bump in the Fuel Graph where it has altered the values, is this normal?

  4. #4
    Join Date
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    You're supposed to blend the Fuel Graph smooth after Transfer Learning To Base. Read 5th paragraph: http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    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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    Thanks I will do that. I have attached a datalog below which shows it happening if this helps:
    https://www.dropbox.com/s/geqhb6u72z...r_0003.dl?dl=0

    And the Config File:
    https://www.dropbox.com/s/7fv932lv1l...se.sniper?dl=0
    Last edited by AMC368; 09-05-2017 at 03:17 PM.

  6. #6

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    Quote Originally Posted by AMC368 View Post
    Hi Dr_grip. Yes it happens after revving in neutral. I'll take a look at the datalog. I have let it Learn an bit and transferred the settings. When I do this, I see a big bump in the Fuel Graph where it has altered the values, is this normal?
    Quote Originally Posted by Danny Cabral View Post
    You're supposed to blend the Fuel Graph smooth after Transfer Learning To Base. Read 5th paragraph: http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    The "bump" is normal. The smoothing is to guesstimate areas of the table that are not yet filled with Learned data closer to what will be the Learned values.

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