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Thread: High IAC readings?

  1. #11
    Join Date
    Dec 2009
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    Connecticut
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    22,684

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    You stated the engine timing (timing light?) reads 10° lower the laptop (EFI software). So this seems like the timing isn't synchronized for some reason. You could put a timing tape on the damper, as outlined in that ignition timing synchronization link.
    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.

  2. #12

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    No, the Holley 3.5" TSLCD reads different than laptop. Which is why I'm confused, because both the laptop and 3.5" TSLCD are getting info from ECU.
    If I go to the ignition Base Timing Table and watch the "bouncy ball", it's different than what the 3.5" TSLCD is telling me.
    For instance, I currently have idle timing set at 22°, the TSLCD would show 10-12°. This applies to both cases with & without Idle Spark enabled.

  3. #13
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    Dec 2009
    Location
    Connecticut
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    22,684

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    Well that's completely different, your original statement was vague. Anyway, I don't know why the two devices don't match.
    Ensure there aren't any active 'timing modifiers' at this point (e.g. Timing vs Coolant Temperature, Timing vs Manifold Air Temperature, Knock Retard, etc.).
    Also, ensure you don't have any erroneously programmed "Warning Enabled Timing Offset" parameters in the "Sensor Scaling/Warnings" (System ICF) or in the custom Inputs (Inputs/Outputs ICF).
    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.

  4. #14

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    Are you sure that you do not have any vacuum leaks? Andrew

  5. #15

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    No vacuum leaks, on initial start I had some. Found cracked intake. After replacing I performed a smoke test to verify, but I found the timing issue. I had the boost icon on. The only thing I had enabled was to shut ignition after 20 psi. I have no clue why that was changing the timing. I removed the boost icon configuration and bingo everything lines right up. I'm still confused why that happened.

  6. #16

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    Now just have one tune issue which I seem to struggle with (even does it in my other car). Upon decel like when I come to a stop the idle drops below commanded level and hunts up & down for a few seconds before smoothing out. Any suggestion on the hunting upon sudden stop?

  7. #17

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    It's always good practice not to load any ICFs that are not actively being used. There's background logic that gets enabled when various ICFs are loaded and if they are not being used, this can cause problems (like you had with the timing). Raise the IAC Hold Position (if you go too high you may get a hanging idle) and/or decay rate. Also, make sure the timing is constant in the idle area. What kind of cam are you using? What kPa does it idle at? Andrew
    Last edited by andrewb70; 06-03-2019 at 06:53 PM.

  8. #18

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    Ya, I thought the boost shut off would be good on the Boost ICF. One thing I did notice was the it kept telling me I had a Unassigned Input/Output on Pin Map (for dome pressure), but I wasn't using that and couldn't get it to remove without removing the whole ICF. The cam is a Jegs .588"/.588" 228°/230° 112°. And a cast 7875 turbo. Thanks Andrew, I'll mess with the IAC Hold & Decay Rate see if that helps.

  9. #19

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    You can also try different idle control strategies. There are a number of ones to choose from. You're probably using GM LSx right now. Try the "Slow" setting. It might work better for you.
    IG @projectgattago

  10. #20

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    I'm using GM LSx. I did try Slow when tuning idle, but seemed to do better with LSx, but not a lot of difference. Or would that be more of a function of my after decel hunting issue?

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