Is your car a CA model? Even if not I sometimes wonder if people are checking the duty cycle properly.

www.landiss.com/mixture.htm

has a very good write-up on how to check if your car is 49-state or CA and then set the system to "test mode" if necessary and procede with checking duty cycle.

Anyone interested in checking duty cycle should print these web pages out, read, and thoroughly understand how to do this procedure. Otherwise you may get false readings.

Duke