Lumpy idle.

Discussion in 'Engine/Drivetrain' started by Boonies, Jun 27, 2011.

  1. Boonies

    Boonies Member

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    So this is a 1974 18RC motor. Had the shop go through her and check the timing, points and tune the "last" carb. But that unit will not drop down from the 12k idle and thus will be going back to the rebuilder.

    Now the new carb is on with no vacuum leaks, idle drops down just fine but once i got the idle to the 750/800rpm range it seem a bit lumpy.

    Here is a short video of the motor idling.

    Thoughts and opinions?
     
  2. Radioflyer90

    Radioflyer90 Newbie

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    Well, that idles smoother than my 8R-C, I've always heard that rough idle was part of the territory with these engines. My dad used to keep the idle down around 650 rpm and the engine wobbled all over the place. I tuned it up and brought the idle up to 800 which made it much easier to live with, but it is still lumpy.
     
  3. dillinja666

    dillinja666 Toyotaholic

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    ya they dont idle as smooth as a 22R or anything like that. im at work so i cant see the video, but from the 2 8rc's ive had over the years i remember the idle qualify was horrible. how does it drive? does it rev smooth with out hesitation?
     
  4. Boonies

    Boonies Member

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    Well at the moment she drive just fine and dandy, no hesitation off idle but once you get over 30mph and then come to a stop(or put her in neutral) the motor dies out. If you keep her about 30 or bellow no problem what so ever. Have the carb adjusted to 2.5 turns out on the fuel/air screw and idling around 800rpm at the moment. I was trying to see if kicking up the idle would keep her from dying.

    Long story short, this is my second carb on the motor, both rebuilt. The first one didn't have these issues but the throttle wouldn't drop down to idle unless you pushed the linkage or pulled the throttle pedal level. So on to the current carb which like to die out on idle.

    Fuel pump squirts 4.5 PSI and i need to do a compression test tomorrow to see if one of the valves is burnt. Guess a vacuum test wouldn't hurt either, is there a spot on the intake manifold to hook up a vacuum gauge?

    Found one vacuum leak but will recheck for more.
     
    Last edited: Jul 8, 2011

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