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308 idle with A/C

Discussion in 'Technical Q&A' started by olehholy, Jul 26, 2005.

  1. olehholy

    olehholy Karting

    Nov 12, 2003
    118
    NJ
    Full Name:
    Oleh Holynskyj
    My 308QV is struggling to hold idle with the AC on ........ sometimes. At first I thought maybe it was fuel or ignition-related but those parts of the car check out OK.

    In troubleshooting, I am beginning to suspect that the problem is electrical as suggested on some related threads. I recetly discovered that the reason for "somtimes" was that the trouble would start on a very hot day when BOTH the AC and the radiator fans were on. Since these are both high-draw current items I suspect there is excessive current draw. The alternator and batt are both relativly new (less than 2 years), and I dont suffer any of the obvious charging system related symptoms.

    I realize that asking if there are any other weakpoints to the 308 electrical system is like asking if there are any trees in the forest, but I was wondering if anyone had a similar problem and could steer me to a part of the system that can result in this phenomenom.

    Thx,

    Oleh
     
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  3. greg328

    greg328 F1 Rookie

    Nov 17, 2003
    4,135
    Austin, TX USA
    Full Name:
    Greg
    I'm dealing w/ the same problem--77 308 GTB. I think my idle is too low.
    It's about 750rpm w no A/C. Lugs down to about 600rpm with A/C on.

    Can anybody provide ideal rpm targets for both conditions for a 308? Is it different across the model range?


    Greg
     
  4. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,366
    NY
    Greg the normal idle is 1000rpm. I bump mine up to 1100rpm so the compressor draws the 100 rpm. Your idle is to low.
     
  5. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,265
    USA
    Full Name:
    Hugh G. Rection
    Yup, idle is set too low. On my 78 308GTS it was set right around 1000 rpm, and when I ran the A/C it would drop to around 900 rpm. As suggested, you might even what it around 1050 or 1100.
     
  6. greg328

    greg328 F1 Rookie

    Nov 17, 2003
    4,135
    Austin, TX USA
    Full Name:
    Greg
    How difficult is it to adjust idle on a 77 308 w/ carburetors? I'm willing to try to do it; I just don't want to screw up the perfect carb synch I have right now. My mechanic said he'd do it and charge me 1/2 hour labor, but I'd like to give it a shot if it's pretty simple....


    Greg
     
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  8. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,265
    USA
    Full Name:
    Hugh G. Rection
    I had my mechanic do it....took him less than 10 minutes...then we walked next door to the Italian restaurant and I bought him lunch! :)
     
  9. marks308GTB

    marks308GTB Karting

    Jun 6, 2004
    114
    Los Altos Hills, Ca.
    Full Name:
    Mark S.
    you can adjust your overall idle speed in 1 minute if you have a long screwdriver and know which screw to turn.

    I use the one screw on the left-rear carb that drives the overall linkage. seems to work ok. does not upset the synch.

    set for 1050 rpm without ac compressor on. drops about 100 when compressor is on.

    Mark
     
  10. papparazzi

    papparazzi Rookie

    Nov 12, 2004
    43
    Carlisle, MA 01741
    Full Name:
    Christian Delbert
    When I come to a stop, about 33% of the time the engine stalls because the rpms are too low. How do I set the rpm higher on a fuel injected 308??
     
  11. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,001
    Groton, MA
    Full Name:
    Verell Boaen
    Open the bypass air (idle speed adj - large socket head bolt that angles into the throttle body) to increase idle speed. It's fairly sensitive, so go slow.

    On the 328s the bypass air adj is located down on the left side of the fuel distributor.

    BTW, I set my idle @~1000rpm, & it drops to about 875 w/AC on & both fans running. Dash tach reads slightly differently from my digital tach/VOM.
     
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  13. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,687
    North shore, MA
    Full Name:
    THE Birdman
    If you don't evenly adjust BOTH throttle stop screws for the idle adjust, you will make the front and rear banks of carbs out of synch, if only slightly. It may disturb your off-idle throttle reponse, but it may not, depending on how much you tweak the idle screw. The proper way to do it is to pull the cover of the airbox off (not the whole thing) and use a synchrometer to measure flow while you adjust the front and rear throttle stop screws. The trick is that to reach the front throttle stop screw with the airbox in place, you will need a long screwdriver, a mirror, and a little experience to know where it is. However, this whole adjustment can be made in about 10 minutes with the right tools. Of course, if the carbs aren't in good synch to begin with, you are better off just pulling the airbox entirely and doing the synch job right. That will only take an hour or two. I wrote a how-to thread on that. Search the archives.

    Birdman
     
  14. jwise

    jwise Formula Junior

    Apr 2, 2003
    781
    Portland Maine
    #11 jwise, Jul 27, 2005
    Last edited by a moderator: Sep 7, 2017
    Here is the idle adjustment screw for fuel injected 308's. Some adjusters have a hex head instead of the knurled head as shown. It should spin/adjust easily by hand. If not, take it out completely (with the spring) and clean it up and reinstall with a little lubrication on the spring and threads.

    Small adjustments can make a big change.
    Image Unavailable, Please Login
     
  15. greg328

    greg328 F1 Rookie

    Nov 17, 2003
    4,135
    Austin, TX USA
    Full Name:
    Greg
    Can anybody post pics of the pertinent parts for a 308 carb idle adjustment?

    Thanks,
    Greg
     
  16. greg328

    greg328 F1 Rookie

    Nov 17, 2003
    4,135
    Austin, TX USA
    Full Name:
    Greg
    ***bump***
     

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