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Thread: Car accelerating without touching the throttle.

  1. #1

    Default Car accelerating without touching the throttle.

    Hi All. Hoping this is an easy fix. I've just installed the Sniper unit on my '69 Camaro (383 stroker). I've driven it around 200 kms and it was running fine. Now all of a sudden when I take off under light throttle at the lights it starts to accelerate heavily for 2-3 seconds whilst my foot isn't on the pedal. Can be quite dangerous with cars in front. Any ideas? Appreciated. Rob

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    20,954

    Default

    Ensure your IAC Hold Position isn't set too high. The TPS Position should return to 0% with your foot off the throttle.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 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

    Default

    Thanks. Yep, it's definitely at 0% with my foot off the throttle. It doesn't happen when I'm really gentle with the throttle. But under normal driving conditions it will happen.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    20,954

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    To eliminate the IAC valve as the cause, temporarily block off the IAC air inlet port with a strong piece of tape.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 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

    Default

    Might be the rear butterflies sticking open a little. But you can't tell that by just looking at the TPS as it will read zero as it's attached to the front butterflies. A lot of folks have had to put another wrap on the secondary shaft return spring, due to them not closing all the way at times; me included.
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  6. #6

    Default

    Please let us know if you resolve this. Sounds scary.

  7. #7

    Default

    Sounds a little like what happens with my IAC opening up for no apparent reason. Once in a while mine will start to accelerate for a couple seconds with a big "hiss" as the IAC opens. Haven't found a cause yet and is easy for me to deal with by pushing in the clutch. An automatic transmission would be a little different.
    https://forums.holley.com/showthread...tall-quot-mode

    Anyway, keep your display on a screen that shows your IAC Position, and take note if the IAC valve is opening when this happens. That will at least narrow the cause way down. B.

  8. #8

    Default

    Hi guys. Sorry for the delay in getting back. I've checked the IAC at idle and its at 2-10%, and while driving at 30%. (I've also tried dropping this to 0%, but it didn't make a difference). I've also tried resetting the Wizard, but haven't tried blocking it off yet. I've got a datalog, is it possible to upload it here? It'd be great if someone on here can see something and it's just a simple setting. Appreciated, Rob
    Last edited by gdbst1; 04-07-2019 at 03:19 AM.

  9. #9
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    20,954

    Default

    Quote Originally Posted by gdbst1 View Post
    I've got a datalog, is it possible to upload it here?
    Originally Posted by Danny Cabral
    For further assistance, post your Config File and a short datalog of this occurrence for us to analyze.
    Also, review the datalog and inform us of exactly where in the datalog (time/seconds) the problem occurs.
    Datalog & Global Files can be linked to a document hosting website. I use Dropbox.com.
    Files can also be "zipped" (compressed zipped folder) & attached directly to a forum post ("Go Advanced" & "Attachments").
    Your Config File is in the "Documents", "Holley" folder, "Sniper" folder, "Config Files" folder (.hefi file).
    Your Datalogs are in the "Documents", "Holley" folder, "Sniper" folder, "Data Log" folder (.dl file).
    Someone will analyze/troubleshoot the problem & offer advice.
    https://www.youtube.com/watch?v=iqHOtDNiTNA (How To Record & Email A Datalog)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 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
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,194

    Default

    Post the Config File with the datalog.

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