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Yet another carb or idle question

Discussion in 'Mitsubishi Minicab' started by drewdaddy, Sep 1, 2014.

  1. drewdaddy

    drewdaddy New Member

    Yes I searched. Not sure of the year (can't read the torn seat belt tags) 1991-1998 u42t 3g83 minicab. The problem I'm having is the truck lopes at idle. As in revs uuuuuup doooown uuuuuup doooown. Over and over. Now once I put it in gear and drive it runs perfect. Only has this up down in the rpms at idle. I don't want to get stranded somewhere. I'm going to check the carb and dig into vacuum lines today. Just was hoping someone could point me in the right direction. I have already ran fresh non ethanol gas and seafoam through the system. Thanks
     
  2. drewdaddy

    drewdaddy New Member

    Think I got it figured out. Between adjusting the idle screw and the fuel to air mixture screw on the carb it is almost purring. A full tune up kit is in the mail to get everything fresh.
     
  3. Please check a vacuum line first.
    and, Cleaning of a throttle body....
     
  4. drewdaddy

    drewdaddy New Member

    Thanks for the info, seems like vacuum lines are a major problem with these trucks.
     
  5. muddy moose

    muddy moose Member

    When you check the vacuum lines, make sure they fit the nipple TIGHT. If the slid on and off easily they will leak. I had a mystery leak that was literally as simple as cutting a half inch off and putting it back on. I thought thy were all snug and that ment they were ok. Not the case. Snug isn't tight, and is noticeable hahaha
    Also........ before I turned any screws on the carb, I would pop the top of the carb off and clean everything as well as the bottom. That way your not just postponing a bigger problem at the most inopportune time. Good luck
     
  6. drewdaddy

    drewdaddy New Member

    I'm going to try that. I have it to where it idles good. However I noticed last night when I turn the lights on or blower motor it goes back to idling up and down. The load on the motor from the alternator has it idling rough. I really think it's a vacuum line also.
     
  7. muddy moose

    muddy moose Member

    It is. Their is a vacuum line that runs to a hi idle actuator for when you turn on lights or heater. It brings the idle up so that the added load doesn't kill the engine. I'd check all of the vacuum cans on your carb. The diaphragm might have a hole in one or a cracked vacuum line. Once you get that hammered out........ find the thread on adjusting your carb on here. It's very detailed and should get ya set. Buy check those vacuum lines and all the little vacuum actuators.
     

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