Poor fuel economy in 86 Fleetwood RWD with Olds 307
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5.0 and 5.7 Discussion, Poor fuel economy in 86 Fleetwood RWD with Olds 307 in Cadillac Engine Technical Discussion; Just bought a 86 Fleetwood Brougham with 88,xxx original that was well taken care of and maintained by the dealer.The ...
  1. #1
    fullpwr5516 is offline Cadillac Owners Member
    Automobile(s): Fleetwood Brougham
    Join Date
    Mar 2013
    Location
    St.Louis,MO
    Age
    38
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    4

    Poor fuel economy in 86 Fleetwood RWD with Olds 307

    Just bought a 86 Fleetwood Brougham with 88,xxx original that was well taken care of and maintained by the dealer.The car was sitting for around 7 years in a garage until I stumbled upon it.I removed and flushed the fuel tank and filter,put a new battery in and she fired up like she was only sitting for a day.it has the Olds 307 with a Q-jet carb.Engine idles fine,does not smell rich and no visible smoke.No engine light and no difficulties starting.All of the vacuum lines appear intact and all sensors plugged in.I know these cars won't have the pickup of a big block but this thing will barely get out of its own way on any kind of grade.Also getting about 11 to 13 miles per gallon when I believe these were advertised as 18 to 23.Anyone no of some obvious things that could be causing these issues? Thanks

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  3. #2
    brougham is offline Cadillac Owners Master
    Automobile(s): 1991 Cadillac Brougham D'Elegance 5.7 Litre
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    Jun 2003
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    Canada
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    Re: Poor fuel economy in 86 Fleetwood RWD with Olds 307

    If you're driving in the city with that mileage it's about normal. It should be better on highway.
    Those cars aren't known for their speed. Going through the carburetor making sure it's adjusted properly or even rebuilding it if it's never been done before might help a bit.

  4. #3
    timswhite88 is offline Cadillac Owners Member
    Automobile(s): 1988 Brougham - white with white top.
    Join Date
    Mar 2013
    Posts
    1
    Quote Originally Posted by fullpwr5516
    Just bought a 86 Fleetwood Brougham with 88,xxx original that was well taken care of and maintained by the dealer.The car was sitting for around 7 years in a garage until I stumbled upon it.I removed and flushed the fuel tank and filter,put a new battery in and she fired up like she was only sitting for a day.it has the Olds 307 with a Q-jet carb.Engine idles fine,does not smell rich and no visible smoke.No engine light and no difficulties starting.All of the vacuum lines appear intact and all sensors plugged in.I know these cars won't have the pickup of a big block but this thing will barely get out of its own way on any kind of grade.Also getting about 11 to 13 miles per gallon when I believe these were advertised as 18 to 23.Anyone no of some obvious things that could be causing these issues? Thanks
    I just bought an 88' Brougham and don't remember them being so slow off the line. They advertised 18/23 when the car came out... Maybe it was 17/23, but the driver before me logged his mileage etc and he averaged 13.2 mpg for 3 years.

    I just bought it 2 days ago with 79,400 miles for 3k. The RWD just MAKES this car handle like a dream.... A floating dream.... (Not a 911) but very controllable.

    An oil Change and engine cleaner - buy "seafoam".... It's $10.99 ($7.99 this week at advanced auto, but regardless, this stuff will clean your internals and make your car runner smoother and with better mileage before you've driven 10 miles. Buy 2 cans, so you can put 1/2 a can in the oil as well. It helped me and I'm getting close to 15 with all city driving.

    Getting a complete tuneup today and ill report back how it does.

    I bought my first caddy in August.... A 2000 Deville base with 185,000 miles and just sold it with 198,000. Engine was great.... Electronics were going bit by bit and you could tell once they were gone - so was the car. So I went back 12 years and bought an 88' Brougham with 79,400 miles for a great price..

    More to come.... All advice welcome.

    Tim

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