83 Seville HT 4100 throttle?
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HT4100 4.1, 4.5, 4.9 Discussion, 83 Seville HT 4100 throttle? in Cadillac Engine Technical Discussion; I'm thinking of buying a 1983 SEville with the HT4100 and about 106K miles. when I was driving it around ...
  1. #1
    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
    Automobile(s): '75 Sedan DeVille
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    Oct 2012
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    Texas
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    83 Seville HT 4100 throttle?

    I'm thinking of buying a 1983 SEville with the HT4100 and about 106K miles. when I was driving it around the parking lot today, I noticed the gas pedal would seem to make the car lurch, in other words, when I had my foot off the gas pedal, it would accelerate on its own, as if I were pushing the gas pedal down. This car hasn't been driven much in the last few years, needs a tune up, also it seemed there was some smoke coming from the rear passenger side of the engine. Any ideas what the acceleration issue could be? throttle body? something with the computer?

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: 83 Seville HT 4100 throttle?

    This car has a ISC ( idle speed control) motor on the driver side of the throttle body. Looks like a fast idle solenoid from the 70's. Most are either misadjusted or broken and no longer retract or extend to control the idle. A simple 3 bolt replacement but you must have the factory service manual to adjust it. The smoke is probably a valve cover seeping. In 83 the cover was sealed with RTV silicone. Most times the prior owner changed to cork and the gaskets cracked or loosened. Remove the oil fill cap and make sure the underside is dry, no light chocolate brown color indicating coolant leaking internally. Verify the rear brakes work by holding the parking brake pedal with your left foot very firmly and your right foot firmly on the brake pedal in gear. Now gently lift up on your right foot. The car should NOT move at all if the rear calipers are working. If it moves, it needs 2 rear calipers.

  4. #3
    shwhitley's Avatar
    shwhitley is offline Cadillac Owners Member
    Automobile(s): '75 Sedan DeVille
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    Re: 83 Seville HT 4100 throttle?

    Thanks! I will check all of that out!

  5. #4
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
    Automobile(s): 1985 Sedan DeVille
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    Re: 83 Seville HT 4100 throttle?

    Disconnect the cruise control linkage. If its setup wrong, the engine vacuum will tug on the rod at idle.

  6. #5
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
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    Re: 83 Seville HT 4100 throttle?

    ehall, A new member, WWII is trying to contact you regarding this idle speed problem. I sent him a Visitor Message - hopefully he'll see it and post here.

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