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Thread: '90 SC Running Cold/kiw MPG

  1. #1
    Join Date
    Dec 2015
    Location
    Daytona Beach, FL
    Posts
    223

    '90 SC Running Cold/kiw MPG

    As you guys might remember, about a year ago I replaced my entire AC system, and my cooling fan motor. Ever since then, the engine has been running really cold, especially when the AC is on. I think this is causing the car to run rich, and my MPG hasn't been the same ever since (I've been averaging MAYBE 16mpg on Shell V-Power 93). I don't have a lead foot, and I don't really send it into boost very often, so this MPG really is weird. It really only gets up to temp after like 20 minutes running with the AC off (no cooling fan running). But when I'm running the car with AC on (cooling fan on), it never really gets above the "N" on the gauge. I know my new AC condenser is ALOT thinner than stock (providing better airflow). I think maybe this is confusing the computer, messing up my air/fuel ratio. Am I worried over nothing, or is this an actual problem I need to deal with? I still need to do a full tune up on it and hopefully that will improve MPG, but I figured I'd run this past you guys beforehand.

    Edit: Typo in the title, meant to say low MPG
    Last edited by Roboplex; 05-23-2018 at 07:42 AM. Reason: Typo

  2. #2
    Join Date
    Sep 2003
    Location
    Elizabethtown, KY
    Posts
    35
    Sounds like you might need a thermostat.

  3. #3
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,204
    Also, there's a TSB on the sending units failing causing them to read LOW.

    I'd check the thermostat housing and the radiator with a non-contact thermometer and see how hot they're actually getting.

    RwP

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