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First, the easiest way to adjust your CO is definitely Rod's method. YOU DO NOT NEED TO DISCONNECT THE O2 SENSOR... It does not apparently correct the mixture dynamically at idle. Hole # 5 in diagnostic connector hooked to a powered analog voltmeter, with the negative lead grounded anywhere that works. If you are close to proper setting, and car is warm and sensor is working, you will get an oscillating voltage switching between 0 and 12V. If the mixture is perfect, the oscillation will be perfectly even, like a pendulum. AS you turn the screw (AFM bypass screw) you will see that the oscillation starts to hang out longer at either end. Then, it stops oscillating alltogether. SO you just slowly mess with the screw until you see the pendulum.
Now, if your mixture is way off, the screw won't do squat, and the meter will just stay pegged at 0 or 12 volts. A fried sensor would cause this too. But in my case, I have been messing a little with the spring in the AFM, and I had it four notches looser (richer). No amount of screw turning would get it to oscillate, it was way out of range. So I found that I had to adjust the spring 2 notches TIGHTER than it was originally set, and then I got oscillation. A little screw turning evened it out.
I confirmed that this worked by reading the O2 sensor voltage directly in both open and closed loop, at idle and driving. Even in open loop, when I had the AFM and CO screw adjusted right, I got very good readings. 0 volts at coast off, 0.9+ volts at WOT, and oscillating around 0.5V while cruising. In closed loop, very similar, but the oscilations become very regular and very centered around 0.5v
So this was all a good bit of fun, and now I know that things are adjusted to spec. Still doesn't solve my cold driveabilty issue. Anyway, I hope to post some account of all this on my website.
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