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Thread: How tight should secondary return spring be?

  1. #1
    Join Date
    Jan 2012
    Location
    Illinois
    Posts
    4

    Question How tight should secondary return spring be?

    I was having weird high idle problems. After a longer time period than I'd like to admit, I realized that it happened only after applying hard throttle, and noticed that the return spring on the (~10 year old HP EFI) TBI secondary throttle plates was knocked off at some point, probably when I pulled the engine last. 🤦*♂️

    In its neutral position, the spring leg that goes on the throttle arm points down. So, 1/4 turn re-seats the spring. Thinking that was probably a bit loose, I twisted the coil a full revolution (well, I guess 1.25) and then hooked it on. Seems to work and feel OK, but I can't find anything that tells if I should try to crank it around again, or if it was right at the lower tension 1/4 turn, or what. Help?

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    22,400

    Default

    If you're referring to the coiled shaft spring, as tight as your finger allows comfortably. (They're usually one turn too loose from the factory.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, 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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    Jan 2012
    Location
    Illinois
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    Default

    Yeah, that's the one. Being loose from the factory would explain how it popped off in storage.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
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    LOL, we figured it out. Is this the older 900 cfm throttle body (LINK)?
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, 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
    Join Date
    Jan 2012
    Location
    Illinois
    Posts
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    Default

    Indeed it is. Related: Here's a short video I made while I was trying to figure out how the way-too-rich idle (bad WBO2 sensor from a leaking header) was behaving using the Galaxy S10's "super slow mo" video mode: https://www.youtube.com/watch?v=WTRmJBFkgIk. Watching the vacuum lines bounce around is almost as neat as seeing how the injectors fire. I need to repeat that now that I have the idle working properly.

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