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Thread: Can't account for ignition timing.

  1. #1

    Default Can't account for ignition timing.

    Looking at a datalog and I can't account for how/why timing is being retarded. This is during deceleration at 0% TPS. The Ignition Timing is 8° less than Base Timing. Any ideas what else could be pulling timing? 8° is a lot!
    Timing vs. Air = 0
    Timing vs. Cool = 0
    Knock Retard = 0

  2. #2
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    It's the Idle Spark control. You can temporarily disable it (Idle ICF) to verify this. Try lowering the RPM Above Idle To Re-Enable Idle Control (although it's doing what it should on deceleration/return to idle), or increase ignition timing advance in that deceleration area of the Base Timing Table.
    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.

  3. #3

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    This is happening around 2300 RPM which is way above idle. Idle Spark control shouldn't be triggering yet, should it?
    RPM Above Idle To Re-enable Idle Control = 200 RPM
    RPM Above Idle To Start Ramp = 1500 RPM
    I was looking for a simultaneous event with another parameter and I notice it happens at the same moment IAC becomes 0% (at least with the two examples I datalogged).

  4. #4
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    It's the Idle Spark control. You can temporarily disable it (Idle ICF) to verify this.
    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.

  5. #5
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    Retarding timing & IAC at close to 0% would be normal ECU function to help engine braking.
    Imagine what your 0% throttle would be like at 2000 RPM, IAC at 10% & 30%.
    The vehicle would have poor engine braking, so you would be on the brake pedal more often. Gary
    Regards, Gary

  6. #6

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    Quote Originally Posted by Danny Cabral View Post
    It's the Idle Spark control. You can temporarily disable it (Idle ICF) to verify this.
    I don't doubt you, but the big question is why is it going into idle spark control? It's causing the engine to buck.
    Sorry for the multiple posts. I keep deleting the post with the mobile app by accident.

  7. #7
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    Quote Originally Posted by Qwktrip View Post
    I don't doubt you, but the big question is why is it going into idle spark control?
    Because during deceleration, the ECU is in Idle/IAC Ramp Down mode (for reasons Gaz64 mentioned above). See post #2.
    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. #8

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    It's a flaw in a system that doesn't require knowledge of the vehicle's speed/gear position. No OEM setup does this. I noticed this in a datalog of mine this week and thought "well this is a stupid, but unavoidable consequence of not knowing vehicle speed or gear position."
    Last edited by Cougar5.0; 10-02-2019 at 09:06 AM.

  9. #9
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    There are ways around it, such as an Advanced 2D Table - Timing Offset type.
    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. #10
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    Quote Originally Posted by Cougar5.0 View Post
    It's a flaw in a system that doesn't require knowledge of the vehicle's speed/gear position. No OEM setup does this. I noticed this in a datalog of mine this week and thought "well this is a stupid, but unavoidable consequence of not knowing vehicle speed or gear position."
    Yes, that's exactly correct. Stalling coming to a stop is the first complaint when a VSS DTC (Diagnostic Trouble Code) is set in some cars. Gary
    Regards, Gary

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