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Thread: IAC got stuck again.

  1. #31

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    With really long datalogs like that, it can be a bit more difficult to pin down the small things because you can't really tell what the driving conditions are a lot of the time. For example, there are several spots where the TPS is reading 0%, but the RPM are over 2,300. That may be decelerating? The IAC is not ramping down (is at the 30% Hold Position) so I assume not. Is that a time where you think the IAC was stuck? 140-142 seconds is one spot.
    69 Camaro
    400 SBC, ProCharger D1SC
    1.302 60', 5.95@116.4 on pump gas

  2. #32

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    Thanks for looking Greg. Yes, that is decelerating. There are a few long descents near my house. IAC will go to Hold Position on long descents sometimes. Other times, it goes to zero. I find that when it’s giving fuel on descents, IAC will stay at Hold (30%), AFR will be around 12:1 and timing control will be near base timing (25°). When it decides to not give fuel (usually after 15 seconds or so of downhill coasting), AFR will be 20+:1, IAC will be at zero and it’ll pull timing down to 17°. These events only happen downhill. I should mention that it never pulls timing in the flats or climbing. I was wondering more specifically if the AFR line looks noisy, or if the frequency of movement in a given time frame seems normal?

    I should also note that I do not have Decel Fuel Cutoff enabled. I was thinking about increasing Minimum Injector Opening Time to correct going lean on long coasts, but I was going to ask that question after determining that other parameters seemed normal. Thanks Again!

  3. #33

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    Your AFR is a little bit more "jumpy" than mine, but I noticed your Target AFR table has a lot more variance in it than mine does. So when you're cruising along the Target AFR is frequently changing as the actual spot on the chart changes.

    For example, at a MAP of 44 kPa you have 10 different Target AFRs between idle and 4,900 RPM. Not saying that's a bad thing, but just know that your AFR graph is not going to be super flat because it's moving and adjusting to the Target AFR as well. My Target AFR in that entire range is just one number, but I have not yet tried to optimize cruise. I'm focusing on WOT for now. It looks like your AFR stays within +-0.5 of target when cruising in Closed Loop.
    69 Camaro
    400 SBC, ProCharger D1SC
    1.302 60', 5.95@116.4 on pump gas

  4. #34

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    Makes sense. I appreciate you taking a look for me. I basically copied Danny’s and toned it down just a hair to be on the safe side.

  5. #35
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,459

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    On deceleration, it'll keep the IAC in the Hold Position until it goes into idle mode. And also, it won't go into Closed Loop on deceleration. You'd need to change "RPM Above Idle To Re-Enable Idle Control" to get the IAC to act sooner.

  6. #36

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    Thanks! I’ll look at that setting. I think by default mine is at 1000 RPM Above Idle and I have my idle set at 750.

  7. #37
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,124

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    "RPM Above Idle To Re-Enable Idle Control", not "RPM Above Idle To Start Ramp".

    Typical IAC Control/Ramp Down Parameter Settings
    Advanced Idle Control: ......................... Slow (Usually the best control.) Sniper EFI users select "Sniper TBI".
    IAC Type: .......................................... Stepper (4-wire), PWM (2-wire)
    IAC Hold Position: ................................ 10%-30% (Usually 15%-20%.)
    Ramp Decay Time: ............................... 1.0-3.0 sec (Usually 2.0 sec.)
    RPM Above Idle To Start Ramp: .............. 1000 RPM (Or higher.)
    RPM Above Idle To Re-enable Idle Control: 50-200 RPM (This setting can be finicky.)
    Startup IAC Position - Hold & Decay Time: 1.0-1.5 seconds (Less is typically better than more.)
    Not IAC, but Idle Spark control usually works well at: 30-40 P Term & 50-60 D Term.
    http://forums.holley.com/showthread....neral-IAC-Info (General IAC Information - Read "IAC NOTES")
    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.

  8. #38

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    Awesome! Thanks for clarifying/typing that out. I really appreciate it.

  9. #39
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,124

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    You're welcome.
    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.

  10. #40

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    So the answer to solving sticking IAC or IAC not following command is making sure no spark plug wires are near IAC. Anytime mine acts weird I've checked and a wire is usually right next to it. Anytime I'm doing an install I'll make sure to wrap wires around back side of distributor cap. Under header wires are nice. I've also run into the 1% TPS, kinda random usually seems to resolve itself, or I just blip the throttle and that fixes it 90% of the time.

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