Here is what I posted yesterday in my thread about idle surge and O2 sensors -
With all the suggestions, I decided to investigate the base idle setting situation.
I started by checking the idle switch by sound and by multimeter, then I checked resistances at the ICV terminals - - all looked good.
I drove long/hard enough to get all warmed up, and watched the idle rise and felt the surging/hunting slowing increasing. I popped in the jumper (BTW a 3.5mm mono jack fits great), and messed with the "screw" shown in the picture below. I was looking for an idle adjustment screw like on an old carb, but there is none. This seems to be the adjustment for the base idle speed.
With the jumper in place, and the O2 sensor connected, the surging was apparent, and I ultimately had to really screw the hex head "screw" in quite a was to get the idle to soomth out in the 800 - 850 rpm range.
Question - what is a good "bench setting" for this screw? Like close to the right, then backoff to the left by X turns.
It seems that mine was very far out, and I rotated it in quite a ways to get the idle where it should be. When I removed the jumper, the RPM dropped 50ishRPM, but seems to be running and idling really well.
So now, with O2 sensor connected, fully warm idle a bit less than 800 rpm, there seems to be no surging and the performance feels really good all around.
I don't know how/why my adjustment ended up so far out, and I hope I havent totally missed the boat on this adjustment.
With the screw - is right/in lean or rich? is left/out lean or rich?
I'll get her out on the road tomorrow to see how things go.
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So, if the idle dropped a bit when I remove the jumper, does that imply I'm not in the sweet spot on the screw adjustment? Should I try to fine tune that, or does it sound like I'm okay?
Like I said, that screw was pretty far out, and as I turned it clockwise several turns, the idle surging went away so that seems like improvement.
My other question relates to where/how to hook up a tachometer/dwell meter in the engine compartment - is there a 12V spot to power up the tach?
thanks for all the ideas!