Idling Too Fast? - Team Camaro Tech
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post #1 of 8 (permalink) Old Oct 5th, 04, 09:56 AM Thread Starter
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Cameron
 
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I have a 69 Camaro with a 400sb with Trick Flow heads, Performer RPM intake, Comp 282s cam, 1 5/8" headers, and a 750cfm vacuum secondary Holley. This car also has cowl induction that pulls outside air in all the time. When the weather starts to get cooler, the idle speed goes up. Right now, I am idling at 1500 RPM most of the time. Sometimes it idles at 900 RPM, just like I want. The throttle linkage is not binding or sticking. I leaned the mixture screws out and that made the idle more eratic and made the car much more jerky when idling around in gear. I can back the idle speed adjustment screw all the way out and I still get a very high idle, most of the time. I am thinking that I am sucking alot of air somewhere, but I have yet to figure out where. Any ideas on what I need to look at next?

49 Chevy 3100 Project
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69 Camaro
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post #2 of 8 (permalink) Old Oct 5th, 04, 10:41 AM
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Jim
 
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Check the secondaries. They may be opened up a little too much. They were on my 750 Vac/sec. You have to remove the carb to get at the adjusting screw. Close the secondaries and turn the screw just enough to crack them open to see light through the bore. This will ensure they don't bind when opening. Another thing to check would be the spring you are using in the secondaries. Sometimes (if you are using a really weak spring)you have to go to a firmer spring to keep them closed and the idle stabil.
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post #3 of 8 (permalink) Old Oct 5th, 04, 10:58 AM
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Where does your choke get it's heat from? is it open all the way? Maybe you're stuck on the last step of the fast idle cam?





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post #4 of 8 (permalink) Old Oct 5th, 04, 04:52 PM Thread Starter
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I have never adjusted the secondaries and I have had the carb since new. But, I do have the weakest secondary spring that you can put in there, and there is no bog when the secondaries open up. I will check and see if they are staying closed tomorrow. Is there any other way to keep the secondaries closed other than installing a firmer spring?

I thought of the choke too, but it is opening all the way and the fast idle cam is retracting with it.

49 Chevy 3100 Project
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69 Camaro
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AutoGear M22 4 Speed
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post #5 of 8 (permalink) Old Oct 7th, 04, 04:05 AM
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There is a secondary throttle stop screw. You can only get at it with the carb off... I would think it would cause an internittent problem tho, or any problem at all unless something is binding in the linkage.

To rule out the secondary's, take the rod off (from the vac can to the throttle plate) and drive it, see if the problem goes away.

** your symptom sure does sound like the choke's cooling off, and engaging just enuf to get u on the first fast idle step...

Get under the hood WHEN ITS HAPPENING, shouldn't be too tough to find whats hanging up... what do you have to push or pull on to make the idle drop back down?

If it's not linkage or choke related, next thing to look at would be a vacuam leak...





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post #6 of 8 (permalink) Old Oct 7th, 04, 12:05 PM Thread Starter
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That's a good idea to check the secondaries out. My choke is electric so I don't have linkage running inside the car to worry about. I was under the hood a few days ago while this was happening and the choke was open all the way and the fast idle cam was completely retracted. I will check again though. For some reason, its been good today, but it has been warmer. It seems to idle fast when it is cooler outside. I'll check the secondaries out sometime this weekend and report back what I find.

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Acro Sport II Biplane
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AutoGear M22 4 Speed
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post #7 of 8 (permalink) Old Oct 8th, 04, 03:37 PM
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hmmm...ok.. fast when the air is cold... cold air is more dense,has more oxygen...long shot, but is your idle mixture set too rich? try leaning it out some, see what the rpm's do..

or perhaps the other way around? vacuam leak? but who ever heard of a vacuam leak only when the outside air is cold?

[ 10-08-2004, 06:10 PM: Message edited by: JimM ]





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post #8 of 8 (permalink) Old Oct 8th, 04, 04:56 PM
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Sounds like a vacuum leak to me. The secondary idle stop is also a possibility and is pretty much the same as a vacuum leak if it is open too far.

The air getting cooler causing the problem to show is probably just a coincidence if you are certain the electric choke is working correctly.

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