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Engine turns after shut-off?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Hayduke, Dec 28, 2000.

  1. Hayduke

    Hayduke 1/2 ton status

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    my rig does this every once in awhile when i use cheap gas. it has a stock 305 w/ 107K miles on it, and it burns a bit of oil too. i forget what it is called....but when i stop and turn her off the engine will chug/lurch/turn a few times, sometimes it's almost violent and scares me! would a good all-around tune up help this? is it a bad thing or is the engine not being beat up too bad? i know if i don't use cheap gas it will go away, but was just wondering. i'm a poor-ass student and with gas prices sometimes all i can fill her up with is crap gas!
    thanks!
    peace.
    HAYDUKE

    Insured By COLT, Policy #.357M

    <A target="_blank" HREF=http://haydukesk5.coloradok5.com>http://haydukesk5.coloradok5.com</A>
     
  2. 87chvy4x4

    87chvy4x4 Registered Member

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    my ol dtruck does this and my dad check it out and said it was cause i had the timing to high

    CaLeB
    RiVeR cItY oFfRoAd
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  3. MudFrog

    MudFrog 1/2 ton status

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    It's called dieseling.

    89 K5 Silverado
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  4. Boss

    Boss 1/2 ton status Author

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    My truck does this when it is idling high and I shut it off. I have a Edelbrock quad carb with electric choke. Eversince I had the electric choke it seems to do this when I don't drive on long trips (and very cold days). So, the carb is still warming up I guess and that means its has to idle high. Then I put it in park and shut her off and it will either make a back fire sound out of the exhaust, or the engine will make a violent sound like you mentioned. Scares me too, but I don't know if any harm is done. I would like to know though. But with my old manual choke Rochester Quad carb, this never happened. Wierd. Anyways, I think that may be why. On longer trips (after the engine has worked hard), the idles goes back to normal and this never happens with normal idle. Anyways that my 2 pennies.
    Boss
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    [​IMG]
     
  5. JimmyDie6.2

    JimmyDie6.2 1/2 ton status

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    check your timing, you can cause serious damage to the vehicle by letting it diesel, if the motor actually backfires your really running a risk. You could bend a valve or a pushrod, check on that timing, crappy gas could also be the problem cheap gas is igniting from the heat of the combustion chamber in addition to timing that is off, without spark. You would need to retard the timing, what this means is turn the distributor clockwise, you need to do this with a light though, to fix the timing properly.......js
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Easy way to solve this (and its only temporary until you get time to really find and fix the problem) is to shut the truck off in gear.



    Dorian
    My K5 and Chev/Olds links: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  7. Cavalry

    Cavalry 1/2 ton status

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    Is your truck kicking to the lowest step on the idle? On a quadrajunk its controlled not only by the choke but a vac pot on the back pass of the carb. Check also for vac leaks. This will make your truck diesel too.
     
  8. Boss

    Boss 1/2 ton status Author

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    dyeager,

    Yeah, I forgot to mention that. Shut the truck off while in Drive, so the idle is still down.

    Now yall are saying that my timing is off, but this only happens when I drive for a short distance (when I start it up when cold) and the carb is still trying to warm itself up. Could this still be the timing? After I drive for a while or drive hard, its perfect. I knew that this could be harmful [​IMG]. Thanks for letting me know.
    Boss
    <A target="_blank" HREF=http://www.boss.coloradok5.com>http://www.boss.coloradok5.com</A>

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  9. NYC K5

    NYC K5 1/2 ton status

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    change the plugs if the plugs are too hot when you shut down the engine they can cause ignition of the fuel. also the grade of gas doesnt matter if your engine is designed for regular it runs best on regular any premium gas you put in is just a waste of money. i run econo gas or 86 octane when i find it and have no trouble.
     

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