What I mean by the duty cycle is the amount of times the O2
sensor goes from lean to rich. I have heard that this can be
set with a led off the lead next to the coil but I must be
doing something wrong. Manuals refer to the Volvo Monotester
but I can't get a decent reading off my dwell meter. I have
looked and have yet to find the definitive method of setting
the O2 sensor frequency, duty cycle, CO level or whatever
you would like to call this adjustment. It appears to be a
necessity for achieving the proper fuel-air mixture.
jd
A dwell meter set for four cyl between the pink test lead and ground,
engine running, will show 53.7*, O2 sensor disconnected. The setting
value should be between 45*-55* engine idling at ~850rpm, warm, throttle
switch contacts closed, dipstick fully seated, no vacuum hose leaks,
ignition showing between 5*and 10* BTDC.
This establishes the mixture setting at idle. All other mixture
corrections during running are regulated by the control pressure and
manifold vaccum changing the height of the air flow sensor plate above
the venturi. There is virtually no correction for restricted injectors,
leaking injector seals, or faulty pressure regulation. The theory being
that if the idle setting is close enough at idle then the converter and
the above mentioned controls will be more than adequate to maintain an
emission level within the regulation in effect at the time.
Bob
