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Thread: High IAC readings?

  1. #1

    Default High IAC readings?

    So been messing with the turbo 5.3L all day. 1st I had fuel pressure readings of 103 psi, after 2x checking everything we found the twin Bosch 020 pumps were over powering the stock 5.3L fuel regulator, disconnected one and put other on boost reference. Any way, it has very high IAC readings. Turning throttle blade set screws in or out I couldn't get it anywhere near 5-10% at hot idle. The only way I could get it in that 5-10% range was by raising the idle timing to 31°, which got the IAC in range, but idle quality went way down. From 15°-28° IAC was anywhere from 25% -65%. Any suggestions? Car seems lazy revving off idle.

  2. #2
    Join Date
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    Default

    Ensure the spark plug wires (or any other high voltage wiring) aren't too close to the IAC motor/wiring. Ensure the TPS Position always return to 0% at idle, or else the IAC Hold Position is activated and raises the idle. A lot of vehicle applications don't like the IAC Hold Position (Idle ICF) too high. Ensure the ECU main power & ground cables are connected directly onto the battery terminals, and your engine block is well grounded (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.

  3. #3

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    I have all my grounds proper and nothing is close to IAC. I currently have IAC Hold Position at 40%. I'll lower that see if anything changes.

  4. #4
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    Yes, lower that excessively high IAC Hold Position.
    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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    Danny, decreasing IAC Hold, wouldn't that worsen the problem with my IAC being high and activating the Hold?

  6. #6

    Default

    Not sure if I understand the question here. The IAC Hold Position is only active when TPS is above 0%. Not a factor in the idle IAC Position.
    '95 Lightning, HP EFI, 351W, S472SX-E, 20 PSI,N2O,pump & W/M

  7. #7
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    As I stated, you want to decrease the IAC Hold Position. Please read the manual definitions for IAC Hold Position.

    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. #8

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    Thanks Danny. I actually got it idling pretty good, and got the IAC down into range. One strange thing I noticed, the other day when I upgraded to V5 the 3.5" TSLCD didn't upgrade. When I was on phone with Holley they told me to download 3.5" V5 firmware and install it. I did and worked perfectly, but it still says V4 and everything lines up with laptop except ignition timing. The timing reads around 10° lower than laptop. Any insight on this? Thinking maybe I should try firmware update again for 3.5" TSLCD?

  9. #9
    Join Date
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    Quote Originally Posted by jasonsnova View Post
    ...and everything lines up with laptop except ignition timing. The timing reads around 10° lower than laptop. Any insight on this?
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Step #4!)
    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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    Danny, I just read through that link I guess I'm a bit confused. In that link, it's all referring to engines with distributors this is on a 5.3L LSx engine, not distributor. I didnt have this issue with my other car. Guess I'm confused.

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