4.9 crappy milage
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 crappy milage in Cadillac Engine Technical Discussion; Ok, most of you probrably wont believe me, but the a/c in my 91 deville deflated during the winter due ...
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    cl1986's Avatar
    cl1986 is offline Cadillac Owners Connoisseur
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    4.9 crappy milage

    Ok, most of you probrably wont believe me, but the a/c in my 91 deville deflated during the winter due to a leak when the service station replaced a part, and because there was no refridgerant in the system it caused poor gas milage some how. I took it in to a dealer and they told me i need to fix the a/c. I didnt believe it either, but as soon as i filled the system up, the milage went back to normal. Anyone else experienced this?? I still cant hardly believe that was the case.

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    VlaDeMaN is offline Cadillac Owners Member
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    Re: 4.9 crappy milage

    i refilled the refrigerant about 3 months ago, but when i got home that day, the line blew as i opened the door to get out of the car. its the one right behind the radiator. anyways, the caddy averages at 17mpg (electronic counter) and i do about half freeway, half city driving. now its even worse cause of the misfire, but that another story (13.4 mpg) do you think fixing that line (junkyard pull) would give me better mileage?

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    cl1986's Avatar
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    milage

    ours gets around 24mpg mostly highway driving, when a/c system empty it got around 13 like your stating. I am willing to bet it would improve it. By the way i might have the part your looking for but im in SD, not sure where you are, might not cost you much anyway.

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    VlaDeMaN is offline Cadillac Owners Member
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    Re: milage

    Quote Originally Posted by cl1986
    ours gets around 24mpg mostly highway driving, when a/c system empty it got around 13 like your stating. I am willing to bet it would improve it. By the way i might have the part your looking for but im in SD, not sure where you are, might not cost you much anyway.
    im in los angeles. i could pay you for it, if u wanna sell it to me, although im going to the junkyard this weekend. whats your deal?

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    Angry Re: 4.9 crappy milage

    my 91 Deville is also getting crappy mileage, it runs great (235k) but the electronic readout average is 11mpg, I make a 32 mile roundtrip to work and im using 4 gallons to do so!! NOT GOOD!!!! Lol any ideas? i was thinkin O2 sensor,

  7. #6
    D148L0's Avatar
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    Re: 4.9 crappy milage

    Quote Originally Posted by caddypimp93
    11mpg, I make a 32 mile roundtrip to work and im using 4 gallons to do so!! NOT GOOD!!!! Lol any ideas? i was thinkin O2 sensor,
    My average, too... what to do??

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    Re: 4.9 crappy milage

    Quote Originally Posted by caddypimp93
    my 91 Deville is also getting crappy mileage, it runs great (235k) but the electronic readout average is 11mpg, I make a 32 mile roundtrip to work and im using 4 gallons to do so!! NOT GOOD!!!! Lol any ideas? i was thinkin O2 sensor,
    If you are using 4 gallons in 32 miles that is 8 MPG....not the 11 on the display. That indicates that unmetered fuel is entering the engine.....most likely cause is the fuel pressure regulator.

    With the engine idling, pull the vacuum line off the fuel pressure regulator and watch the vacuum nipple on the fuel pressure regulator for several minutes for any sign of fuel leaking from it. There shouldn't be any.... Replace the FPR if you see any fuel from the vacuum nipple on the FPR.

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    Re: 4.9 crappy milage

    i get 8-9 with my foot out of it lol

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