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Thread: Engine runs away with cluch pressed in.

  1. #1

    Default Engine runs away with cluch pressed in.

    I have a very odd thing happening. I installed the Sniper several days ago and I have only driven it about 30 miles. Everything appears to be working well. I have the IAC at about 6% when the engine is hot. The vehicle starts and drives well. If I snap the throttle, the engine revs then returns to idle smoothly if the truck is in neutral and the clutch is not pressed in. With the engine hot, and the transmission in neutral, clutch out, the engine idles about 700 RPM. If I press the clutch in, the idle comes up to about 800 RPM. The IAC remains about the same and the TPS shows 0%. With the transmission in neutral and the clutch out, if I press the gas a bit, the TPS will read the throttle movement and the IAC begins to adjust. When I let off the gas, the engine idle returns to normal. If I press the clutch to the floor, then touch the gas a bit, the IAC moves to 20% and the engine begins to race. The TPS still shows 0%. If I let the clutch back out, the IAC reduces and the engine returns to a normal idle.

    The vehicle is a 1979 International Scout II with a 345ci V8 and 4 speed manual transmission. I can't wrap my head around why pressing the clutch is effecting the EFI at all, especially the IAC. Anyone have any ideas?

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    24,172

    Default

    To eliminate the IAC valve as the cause, temporarily block off the IAC air inlet port with a strong piece of tape.
    Ensure your IAC Hold Position isn't set too high. The TPS Position should return to 0% with your foot off the throttle.
    Record & review a short datalog of this occurrence. Pay special attention to the center paragraph in blue print:
    Originally Posted by Danny Cabral
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Config File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley Sniper EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).


    I find the most helpful datalog function, is overlaying the datalog on your Config File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Config File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Config File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    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, 232°-244° duration/.623" lift/114° LSA camshaft, 11.8:1 comp, TFS R-Series FTI ported intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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/3000 RPM converter, FPP aluminum driveshaft, FPP 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 MT tires.

  3. #3

    Default

    I figured it out! After looking at the control linkage, I discovered the clutch rod runs directly under & next to the gas pedal lever. That rod has a slight bow in it. When I press the clutch in, the rod moves over and physically touches the armature on the gas pedal. This causes some friction and the gas pedal does not return properly. Thanks to Got Scoutt for asking about the truck being lifted. That prompted me to investigate that avenue.

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