[psalt]

Bill,

If the idle speed rhythmically oscillates after the engine is fully warm, it sounds like it is going into closed loop. The oscillation is caused by the dithering duty cycle around stoich. If you are still not reading a dithering duty cycle, you need to try a different meter, then test the green/white wire circuit in the test connector. I would not adjust the mixture until you can read the duty cycle correctly. The duty cycle can be calculated by multiplying the dwell reading on the 4 cylinder scale by 90%. An analog dwell meter displays the numbers normally, not inverted, just as described by Probst and in the Bentley manual, and confirmed by many listers on this site.