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High Idle at Startup

Discussion in 'Technical Q&A' started by Shark49, Dec 21, 2005.

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  1. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
    Full Name:
    Nathan
    #1 Shark49, Dec 21, 2005
    I hope someone can help. I did a search for cold start but didnt really see what I needed. Sometimes, not all the time but more lately since it is cold here during the day in the 50 and 60's, when I start up my mondial the revs will slowly rise up to sometimes as high as 2500 rpms and wont go down even after the engine is up to operating temp. I will go out and drive and sometimes it takes about 15 to 20 minutes to get it to go back down to 1000rpms. What do I need to check? I am not sure where the valve is cause the pictures that were posted in other threads were of 308s.
    Thanks,
    Nathan
     
  2. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
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    Nathan
    #2 Shark49, Dec 21, 2005
    And no its not my floor mats.
    Thanks,
    Nate
     
  3. Michael B

    Michael B F1 Rookie
    Owner

    Apr 28, 2004
    3,765
    US of A
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    Michael
    #3 Michael B, Dec 21, 2005
    Nate,

    Sounds as if your CIS injection may need a few parts reconditioned soon. But, before you do that, try an old Porsche 911 trick. Find said idle valve & rap on it with the end of a screwdriver (or any other suitable tool). If the idle drops a bit upon each rap, then take it to heart & replace the darn thing.

    Bet that will do the trick.
     
  4. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
    Full Name:
    Nathan
    #4 Shark49, Dec 21, 2005
    In another post someone talked about using some carb cleaner and wd40 to clean it out but no clue where it is. Also, right in front(behind?) the engine near the trunk is a brass valve looking thing with a knob you can turn that adjusts the idle. What is this for when there is an idle screw up at the throttle body? I couldnt find any info in my manual.
    Thanks,
    Nathan
     
  5. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    #5 snj5, Dec 21, 2005
    my first simple guess would be the aux air valve not fully closing after start. It is on the port side of the engine compartment, in an air hose running ftom the FI unit to the intake manifold plenum.
    I'd take it off and clean and ensure that no obstruction to the valve, or take it to a Mercdes/Volvo dealer and just get the part which is the same on Mercedes/Volvo.

    Second guess would be the warm up regulator - lots of threads on this
     
  6. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
    Full Name:
    Nathan
    #6 Shark49, Dec 21, 2005
    I'm kinda lost! I need someone to point these out to me! I searched and read the threads about the WUR but my car runs like a champ and has no issues other than the high idling.
    -Nate
     
  7. CliffBeer

    CliffBeer Formula 3

    Apr 3, 2005
    2,198
    Seattle, Washington
    Full Name:
    Cliff
    #7 CliffBeer, Dec 22, 2005
    Shark49, as you say, it's likely not the WUR. Rather, as indicated elsewhere it could well be a sticky aux air valve. To locate this, look for a black pipe which connects to the plenum with one end just down stream of the throttle butterfly and the other end just upstream. It works by progressively opening/closing and thereby providing a auxiliary air supply around the butterfly - should also have a couple of electrical wires running to it. Poke around in the area and you'll find it. Good luck!
     
  8. pistole

    pistole Formula Junior

    Jan 31, 2005
    771
    Malaysia
    #8 pistole, Dec 22, 2005
    Last edited by a moderator: Sep 7, 2017
  9. Andy 308GTB

    Andy 308GTB F1 Rookie
    Lifetime Rossa

    Jun 2, 2004
    2,669
    Essex, UK
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    Andy M
    #9 Andy 308GTB, Dec 22, 2005
    My carb'd 308 (1980/81) developed a fast idle for around the first 5 miles or so, last year. This was after many years of happily idling at around 900/1000 rpm when started - only the odd tickle of the throttle being required to clear its throat.

    My garage had tweaked the carbs and inadvertedly 'fixed' the warm up regulator which, unbeknown by me, had been broken for 6 years or so. As I understand, it is a thermostat that rotates as the temperatue rises/drops - in doing so it opens/closes the throttle a smidge, by means of a flat spot on a round plate.

    The car will be getting its annual service fairly shortly. I will ask that the WUR is disabled - I find it intensely irratating the idle not dropping below 2000rpm until the block has got some heat into it.
     
  10. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
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    Nathan
    #10 Shark49, Dec 22, 2005
    I think I found where its at. It looks like its located under the expansion tank on the drivers side of my mondial. I pulled a vacuum hose off of it that went to a white topped bulbous thingy(like my terminology!) next to the valve cover and sprayed some carb cleaner into both..... Today after work I am going to dismantle it and clean it better, if I can get to it.
    -Nate
     
  11. Mark 328

    Mark 328 Formula Junior

    Nov 6, 2003
    510
    Orange, Ca
    Full Name:
    Mark Foley
    #11 Mark 328, Dec 23, 2005
    Last edited by a moderator: Sep 7, 2017
    Shark:
    That is the wrong part..
    There is no vacuum hose going to the AAV. In the 328 it is mounted under the expansion tank see attachments (Part No. 44 in diagram).
    If you squeeze one of the 19mm hoses (heater hose size) connected to the AAV and the idle goes down your AAV is probably stuck. The AAVs are expensive about $250. I just bought one and it didn't solve my problem.

    Some people have fixed high idle problems by plugging the AAV system with a 3/4" dowel in the AAV hose. They drilled a 1/4" or so hole through the dowel and that it will simulate an open AAV. In your case however you had better get the AAV freed-up.

    Mark
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  12. Shark49

    Shark49 Formula Junior

    Mar 31, 2005
    773
    Boone, NC
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    Nathan
    #12 Shark49, Dec 23, 2005
    Mark I PM'd you.
     

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