1977 Seville 5.7 with EFI looses power under a load
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5.0 and 5.7 Discussion, 1977 Seville 5.7 with EFI looses power under a load in Cadillac Engine Technical Discussion; Seeking advice on my 1977 Cadillac Seville... Motor is a stock 5.7 Cadillac 350 with Electronic Fuel Injection. Fuel pressure ...
  1. #1
    Caddiclysm is offline Cadillac Owners Member
    Automobile(s): 1977 Cadillac Seville
    Join Date
    Dec 2013
    Posts
    2

    1977 Seville 5.7 with EFI looses power under a load

    Seeking advice on my 1977 Cadillac Seville... Motor is a stock 5.7 Cadillac 350 with Electronic Fuel Injection. Fuel pressure varies between 38-43 psi, and holds pressure for 30 seconds after the motor is shut off. The engine starts hard and runs excessively rich when cold (regardless of the season). Under modest acceleration the engine loads up and stalls without warning until driven for 15 minutes or so. After stalling, cranking the engine at wide open throttle starts it up running very rich. When reving the engine, it will not accelerate above 3000 RPM. When holding rpm where the engine begins to stumble, it will clear in about 15 seconds and smoothly revs to higher RPMs. At that point, the motor has enough power to gently pull into traffic on local roadways. Loading up and stalling repeats intermittently until the car has driven for 15 minutes or longer. After that the motor runs smoothly, albeit dramatically under-powered. This car accelerates from 0 to 60 in roughly 25 seconds and can barely climb hills or travel at highway speeds. I am torn between a defective fast idle valve heater or malfunctioning injectors. Anyone care to share their advice on how to resolve these issues? Thanks in advance!

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
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    california
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    67
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    Re: 1977 Seville 5.7 with EFI looses power under a load

    Why the double post?

  4. #3
    Zachary Smith is offline Cadillac Owners Member
    Automobile(s): 1979 Eldorado
    Join Date
    May 2014
    Age
    55
    Posts
    8

    Re: 1977 Seville 5.7 with EFI looses power under a load

    This is quite likely the manifold temperature sensor. It doesn't effect much until after the coolant sensor has detected a warm engine. I am too cheap/ couldn't find
    replacements for both sensors. There are many sensors available for "Intake air charge temperature". Do not buy. They are all wrong. They have the newer Negative
    temperature coefficient response. The Haynes manual is wrong. The resistance should rise with temperature, not lower. I have installed "guitar pots" temporarily to test.
    I can know customize my EFI to fool it into whatever mixture I want. I am sure any potentiometers that you can control between 400 - 4000 ohms would work great.

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