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The later CIS used a Lambda system (yours included). There are 4 main components - an exhaust gas O2 sensor, a computer, a 35% throttle position switch, and a frequency valve (FV). The frequency valve reduced the control pressure.
This is incorrect, the frequency valve (FV) does not effect control pressure, it adjusts the mixture in an entirely different manner. The FV is a solenoid valve, like a pulsed EFI injector, that acts as a variable pressure restrictor to control the fuel pressure in the lower chamber of the fuel distributor. It alters the pressure differential across the metering slits and adjusts injector delivery for any given plunger lift. The control pressure remains constant and the airflow sensor does not move. The lambda fuel trim is more subtle, and it controls part throttle, low load cruise mixture with more accuracy. A correctly functioning 81-83 system, once you understand it and have a some experience tuning the open loop mixture, works remarkable well. And it will talk to you.
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Paul
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