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308 Cold Idle Question (yes another one)

Discussion in 'Technical Q&A' started by Pantera1523, Apr 5, 2004.

  1. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Ok before I get flamed I DID check the archives...

    I have an 85 308 QV, as with most of these cars when cold it idles about 2000-2500 RPM. My question is not why it does this but rather for how long?

    I'm assuming that once things reach a certain temperature it should slow back down correct? What temp is that? I drove the 308 to work this morning, started it up in the driveway and it fires up and idles at 1000 RPM. I let it idle about 1 minute or so to get a little heat into it then I slowly headed out of my neighborhood. Get to the stop sign at the end of the street and the when I push the clutch in the car idles at 2000 RPM.

    Does this the whole way to work, which is only 9 miles. I watched the guages and water temp only got to 160 (I think) it was on the hashmark between 140 and 190. It was still idling at ~2000 RPM when I got to work. I assume it just didn't warm up enough on such a short drive. At what temp should the idle settle back to a lower RPM?

    Maybe this evening I will have to go for a longer drive.. to test it out and see if it gets better once it heats up. :)

    Thanks,
    Scott
     
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  3. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    10,479
    San Carlos, CA
    Full Name:
    Mitchell Le
    Na, 9 milies is plenty long to get the CIS to quit idling so high. You need to adjust it.

    My 911SC (CIS of the same vintage) idles at 1600 RPM for the first mile, and then settles down to 1000 RPM the rest of the way.
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Easy to test. Squeeze the hose from the bottom of the Fuel Dist. going under the coolant tank (it connects to the aux. air valve).

    Put the car in neutral, raise the rear bonnet, and while it is running at 2K rpm squeeze this hose. If your AAV is stuck then squeezing the air will cut off its vacuum supply and drop the idle to 1K.
    Try it and see. It will take a lot of hand effort to squeeze it. I normally squeeze and bend my hose over it self, like a garden hose when you are trying to stop the flow of water.
     
  5. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,143
    USA
    Full Name:
    Hugh G. Rection
    As others advised, the cold idle should drop after a mile or two. If it doesn't, your AAV is a little sticky or "lazy" in operation. Do the test as recommended. On my 328 it is located under the expansion tank on the right side...may be the same location on your car.

    It should be on the cold idle from start...not 1,000 rpm, then creep up to 2,000-2,500 rpm. Except when warm, then it would start at 1,000 rpm.

    Check for threads on the auxillary air valve. There is a wealth of info. on testing, repairing and replacing them.
     
  6. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Ok thanks for the info... I saw the other threads that discussed checking to see if it is stuck. I will check mine tonight. I figured it should have settled down after just a short bit.

    Scott
     
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  8. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,741
    Texas
    Full Name:
    Steve Magnusson
    Another thing to check for a "slowly-closing" AAV is that the +12V and ground signals for its built-in internal heater are present when the engine is running after cold start-up -- the thermomechanical actuator gizmo inside the AAV (that actually moves the vane to block airflow) absorbs heat both from the engine itself (a slow process) and from its electric heater (a faster process).

    Are you saying that after a longer run (say 20~30 minutes), it does eventually settle down to a proper ~1000 RPM warm idle?
     
  9. kdross

    kdross Formula Junior
    Silver Subscribed

    Feb 10, 2002
    873
    NJ
    Full Name:
    Ken
    I have a 1985 308QV that had the opposite problem - the idle was at 500 rpm for 10 minutes upon starting the car. After verifying that the AAV was working correctly, I was able to determine that the thermoswitch on the radiator over-flow tank was defective. This switch is part of the fast idle system along with the AAV. I called Algar Ferrari and ordered a new switch and the system seems to be working correctly. I get a fast idle until my coolant reaches about 140 F. If your AAV checks out OK, then install a new thermo switch.

    Ken
     
  10. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Ok it must be stuck open.. driving home from work tonight it was the same 2000 RPM idle the whole way home.

    The little red SLOW DOWN light on the dash came on and went off a few times. I see in the owners manual that means that the exhaust temp is too high. Could this thingy being stuck open cause this condition?

    I haven't had time to investigate yet, I am hoping to look at it Wednesday evening. Needless to say the 308 is gonna be parked in the garage for the next few days.. :(

    Thanks for everyone's help.. I'll update this thread when I figure out more.

    Scott
     
  11. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,143
    USA
    Full Name:
    Hugh G. Rection
    Uh, forgot to mention...but a common reason the idle stays up is the floor mat....I'm serious. Do go and check. Both my 308 and current 328 sufferred from this malady. Nothing a little Velcro couldn't cure.

    The "slow down" light is could be related to the high idle, but not the aux air valve....I'll leave that diagnosis to the more learned "91TR"... :)
     
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  13. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Ok I just went for a quick spin... nope it's not the floor mat :)

    It was better.. it seemed to idle about 1500ish this time. It just seems to run a bit rough for some reason. I've only had the car a week but I know it idled at 1000 last week.

    Something seems a bit off I just can't put my finger on it. On my quick run around the block the SLOW DOWN light flickered on and back off again. I can't imagine I have a problem with the cats, I just had the emissions done last week and it passed with flying colors.

    Anyway I wont be able to mess with it before Wednesday now... Hopefully then I will be able to investigate further.

    Thanks for all the helpful suggestions.
     
  14. Mr Iceman

    Mr Iceman Karting

    Mar 3, 2004
    101
    Canterbury, England
    Full Name:
    Scott
    Idling at over 2000rpm when cold can't be good for an engine. Am I right in thinking that only you guys with US spec have to endure this, to get the cats up to temp quickly and thus reduce emissions. Is there no way for you to adjust the idle to a much kinder ( on the engine not the environment) level.

    just interested
    Scotty
     
  15. jwise

    jwise Formula Junior

    Apr 2, 2003
    781
    Portland Maine
    Also- try some new gas. If the gas in the car is old or maybe slightly dirty- the slow-down lights will flicker. A friends 308 QV had the same thing and new 93 octane cured it. Can't hurt to try it.
     
  16. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Jwise:

    Hmm.. I hadn't thought of that... Maybe I'll head down to Amoco and put some better gas in.

    I can't remember where the current tank came from... I think it was a gas station I stopped at on the way home from picking picking up the 308.

    Scott
     
  17. Wasco

    Wasco Formula Junior

    Dec 9, 2003
    486
    Salem
    Full Name:
    Randy
    Mr. Iceman,

    My manual says my 308 will idle at 3k while cold. Idling at cold is BAD, chances of loading up plugs greatly increase and you have better oil pressure at off idle rpms. Our farm tractors have systems in place to NOT allow low rpm idles when cold.

    Scott,

    What rpms did you reach? I am sure this is not the problem but everytime I have had a high idle situation on anyother car I have had to rev it up to un stick the high idle.

    PS: Let me know when you get tired of hearing about farm tractors!
     
  18. Pantera1523

    Pantera1523 Formula Junior

    Mar 17, 2004
    432
    Virginia
    Full Name:
    Scott Carpenter
    Waso: Um.. I think I was able to hit around 5-6000 RPM but then the SLOW DOWN light started coming on. The idle never reset back to 1000 like it should have.

    That made me nervous, I read in the manual that the SLOW DOWN light is related to exhaust temperatures. I have noticed a definate change in the way the exhaust sounds since I first got the car. I honestly don't know what to make of it. It is really hard to explain, it just sounds um.. louder I guess is the way to describe it. And it makes like a pulsing sound that I do not remember it making.

    Is it possible the Catalytic converter has gone bad? I just had the Virginia State Emissions done a week ago and it passed with flying colors. I think since the I had the emisions test done I have only put like 35 miles on the car... How could it go bad so fast?

    Anyway I discussed this matter with my friend Matt Boyd who also owns a 308 QV. Long story short, I already have an appointment with FOW for the car next Tuesday. :( I figure with the possibility of the cats being messed up I'd rather have it checked out BEFORE it turns out to be something really bad... such as a roasted 308 :( .

    Scott
     
  19. Wasco

    Wasco Formula Junior

    Dec 9, 2003
    486
    Salem
    Full Name:
    Randy
    The only time I have dad cat go bad they have plugged up and caused back pressure on the engine which muffled the exhaust noise. I can't help you on the cats on a 308, mine were gone when I bought the car and since there is NO emmission testing here I am good without the power robbing cats.
     

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