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Thread: Bad Gasoline = Backfiring?

  1. #1
    Blessed be the lowered RickS's Avatar
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    Bad Gasoline = Backfiring?

    Recently filled at the local Sunoco (no Chevron in the boonies) and the car is starting to backfire. Under hard acceleration, it is starts to miss. When the car backfires, the tach dives to zero, and the sound is like a rifle shot. Should I use a bottle of techron or a product to remove water? Or will a new tank of Chevron cure it and not to worry?
    71 914 3.0, 82 SC, ESR 376, RG 307

    "The problem with the world is, the ignorant are cock-sure and the intelligent are full of doubt." Bertram Russell

  2. #2
    The tach diving to zero suggests to me your problem may be ignition, not fuel..
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
    "Now, to put a water-cooled engine in the rear and to have the radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. 1973)

  3. #3
    Righteous Indignation 70SATMan's Avatar
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    I've used Chevron for years because of the Techron and then switched to 76 in the last 6 mos because of prices. No BS but, I get 4-5 mpg better with the 76 gas. I thought it had to be a fluke so I ran a couple of tanks of Chevron and BAM! mileage was down. I'm planning on keeping with the 76 and try running a Techron additive once a month.

    Doesn't really help with your problem I know. Just wondering if anyone else has run into this with Chevron.

    I don't see how the tach diving to zero could be caused by bad gas (instantaneous decrease in rpm while in gear?). Missing yes. Could be debris.
    Michael
    “Electricity is really just organized lightning”

    -Dusty 70S Coupe
    -S Registry #586

  4. #4
    Quote Originally Posted by pwd72s
    The tach diving to zero suggests to me your problem may be ignition, not fuel..
    I agree. I had the same symptoms with bad wiring in the primary circuit.
    Tom F.
    Long Beach, CA

  5. #5
    You may laugh, but I now buy the cheapest gas I can get: Arco. I didn't use it until gas went to $3 a gallon and notice no difference between it and Chevron gas in terms of mileage or performance. Remember that you will get lower mileage numbers as alcohol content goes up (less potential energy in alcohol than gasoline) which may explain mileage differences.
    Kenik
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  6. #6
    Righteous Indignation 70SATMan's Avatar
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    Quote Originally Posted by kenikh
    Remember that you will get lower mileage numbers as alcohol content goes up (less potential energy in alcohol than gasoline) which may explain mileage differences.
    Yep, that's what I attributed it to.
    Michael
    “Electricity is really just organized lightning”

    -Dusty 70S Coupe
    -S Registry #586

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