andy, i am cutting and pasting from an old message on the DML. It is also in the Technical manual with a picture but not a real detailed explanation. if you are standing behind the car use your left hand and reach the front of the engine about half way down. the diagnostice plug is about an inch and a half wide and has a black plastic cover. It is seated in a black metal bracket. you can unclip it from there and lift it up to use it. you will see the male plugs. here is a a cut and paste on setting your mixture: If you have a dwell meter ($35.00) you can get the air fuel (AF) ratio pretty close. 1. Find the diagnostic plug. On the left rear fire wall. Attach the ground from the dwell meter to pin # 2 on the plug. Attach the other wire from the dwell meter to pin # 3 on the diagnostic plug. Set the meter on Dwell. 2. Crank the engine. Let it get warm. This is so that the oxygen sensor is sending a good signal to the Lambda Control unit. (When the engine is cold the computer sends a fixed signal to the frequency valve). You can see this "fixed" signal on the dwell meter. The read out on the dwell meter will be 60% duty cycle or about 54 on the four cylinder scale. When the engine gets hot the computer starts looking at the oxygen sensor and adjusting the frequency valve to adjust the exhanst level. If the dwell meter needle swings high (60% to 70% or 54 to 63 on the four cylinder scale)on the scale when the engine is warm the mixture is set to lean. Turn the AF screw on the distrubter clockwise just a little with a 3mm allen wrench. Remove the allen wrench from the AF screw, cover hole and let the system settle and look at the dwell meter reading. If the needle swings low (29% to 37% or 26 to 33 on the four cylinder scale)the mixture is set too rich , turn the screw counterclockwise to lean the mixture. again, go easy as an 1/8th or 1/4 turn does alot. Your ears will also tell you if you are getting closer to a smooth idle. hope this helps Mike C 2109 > > since i don't have access to an exhaust analyzer for CIS, can you explain > exactly how to infer the CO ratio from the dwell reading? > Andy