Tailpipe O2 Sensor for 911

[Jay Laifman]

I'm providing follow up info for anyone who might come this way in the future.

I'm now in a great spot. 1/8 a turn in either direction is worse. If I rotate 1/8 lean, the car runs less silky smooth. If I rotate 1/8 rich, I would get a light pulsing/flutter on very light constant throttle - very light, but with focus, it can be felt. So in the middle, it is smooth and without the pulsing/flutter, and with great idle.

I was thinking that I needed a CO meter or O2 meter to get this right. But with such a small difference left now, I can't imagine the meter would really help. I will still give it a 1/16 turn each way and live with it for a while, and see if either direction is even better.

Note, I was slightly suspicious that my Throttle Position Valve could be incorrectly positioned and allowing for the richness to occur at idle and also just off of idle, which could be causing the flutter on light throttle. So I used a clamp to stop the gas from flowing out of the TPV. There was no noticeable difference in the light flutter. I'll double check with the pressure gauge at some point.

[glaverbel911]

With your effort your strictly concentrating on the idle circuit. Turning the metering screw affects the entire AFR rpm range.
With what your doing you really don’t know where your under load AFR is. I would first adjust this partial throttle area (2500-3500rpm) which is far more important and then tweak the idle circuit afterwards. This is how I do it on the bench. If the idle does not come into range with the air bypass screw there is another issue. A Possible small vacuum leak is often the case. The Metering plate height and fuel pressures are extremely important too set up first.
These motors tend to run lean and the metering inlet profile is not well tuned for full power without modifications.