CIS Frequency Valve
 

OK,

The car is an 82 SC, CIS with an O2 sensor.

The Bently manual says to check the frequency valve by feeling for it buzzing while the engine is running.

The problem is...I can't tell if it is buzzing or if it is just engine vibrations. For those of you that are sure you have felt it, how severe is the buzzing?

Pulling the relay from the control unit under the passenger seat definitely makes the engine idle rough (all of this was at operating temperature), so I assume that the mixture is being controlled by the frequency valve. The O2 sensor was hooked up.

Since the control unit affects misture through the frequency valve, doesn't the fact that pulling the relay had a noticeable effect while it was in closed loop mean that the frequency valve is definitely working?

Thanks,

Olivier

you got it. no need to look further if removing the relay makes it run crappy. if you really want to hear it, remove the airfilter housing and with the key in the on position, reach in the hole lift the sensor plate arm for a moment. if the sensor plate contact plug has been removed, you can hear it by just turning on the key. don't keep lifting the arm, or you can flood the cylinders.

Thanks, John. One more thing to take out of the tuning equation.

The manual makes it sound like it would be easy to feel, but I could not really distinguish it.

Thanks again,

Olivier