[WVSC]

I just performed a valve adjustment on my 1983 911 SC. I replaced the spark plugs and reset the timing. It seems to be running better, but it is backfiring a bit at idle and at deceleration. On the video I watched, they also recommended testing and resetting the air/fuel mixture by sticking a volt meter in to the O2 sensor and adjusting it until it reads 12 volts. The problem I am having is that I cannot seem to find the 3mm adjustment screw referenced in the video. I have looked and looked in the area that the video references and where it is shown in my Bentley's manual and cannot find it. I guess I need help locating this screw and thoughts on whether this could fix the backfire problem.

Any help greatly appreciated.

Thanks