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Discussion Starter #1 (Edited)
Hi All,

I have an 81 GTV6 that didn't pass smog here in Kalifornia. It was too high in HC on the low speed part of the test.

I was told my timing was off by 2 degrees (but that didn't fail it as Kali says +/-3 degrees is OK). So now that I have a timing light, how do I time it? I'm guessing I should disconnect the vac line.. but then what line should it line up with? It appears the timing is about 5mm right of the "F".

Also, how do you adjust the idle? Mine seems a little low. I was told the 20mm threaded deal on my throttle body is the idle adjustment, and there is a set nut, and a washer in there. I took it apart, verified the washer wasn't cracked or missing. But tightening or loosening the fitting didn't seem to affect my idle speed.

Any ideas?

Thanks.
 

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The idle speed is set via adjusting the vacuum line coming out of the plenum chamber. The line that has the 22mm lock nut on it.Is that what you adjusted?
 

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There are two adjustment points for idle speed. On the throttle body there is a screw to adjust the throttle stop. It may have a plug over it as it should not normally need adjustment - but you never know what's been done by a PO. The throttle stop should be adjusted so that the throttle is just barely cracked open - the actual idle speed should be adjusted with the idle adjuster (where the 22mm nut/lock nut is located).

With the engine warm, unscrew the idle stop screw until the engine stops slowing down (i.e. the stop screw is no longer affecting the throttle butterfly because it is completely closed). Then screw it in slowly until the idle speed just barely responds. The intent is to get the throttle butterfly to be just barely cracked open.

The final idle speed is made with the idle speed adjuster. Inside the adjuster is a rubber O-ring. As the idle speed nut is turned it squeezes/unsqueezes the O-ring making the ID smaller/bigger - letting more or less air into the engine and thus affecting the idle speed. With time the O-ring gets hard and doesn't change size when the adjusting nut is turned. I bought a new O-ring at the hardware store by just choosing one that was about the same size as the old one.

One other item affects idle speed - the AAV (Auxilliary Air Valve). It is supposed to open up during cold starts to increase cold idle speed and close down after a few minutes. The AAV can get gummed up or lazy when they get old. You can try removing it, sloshing some solvent around inside it (a few squirts of carb cleaner) then wash it out with soapy water, rinse and dry to see if that will encourage it to work better.

More info (including setting ignition timing) is in Greg Gordon's L-jet page
 

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idle speed will also change with spark timing adjustment. also, the allen head screw on the AFM can be used to adjust idle co.
 

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Discussion Starter #5
Thanks guys! Yeah, I was looking at the idle adjustment wrong. I didn't think that if I tightened it enough, I would narrow the hole! I see that now.

I'll tighten it a bit more, and see what that leads me.

Thanks!
 
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