Idle fluctuates between 600 and 1500 rpm

[sweetp01569]

I need some help from anyone who might recognize the issue I have. My idle was nice and stable until I took a ride today. When the car warmed up, the idle fluctuated between about 600 and 1500 rpm, up and down, up and down - very annoying and it almost wants to stall out. However, this may offer a clue - if I disconnect the power connector or the middle vacuum hose on the ignition solenoid valve, the idle smooths out. There is vacuum on the middle rubber hose. The solenoid valve clicks on and off with the idle microswitch. The frequency valve hums and buzzes appropriately. Does anyone have a clue what might be causing the idle fluctuations?

Thanks,

Paul
Vin 10944

[Bitsyncmaster]

My first suggestion to try is to turn the idle switch screw in a little and see if that helps. If your getting intermittent advance it can show those RPMs you stated.

[sweetp01569]

Thanks Dave. Are you talking about the microswitch screw? At idle the switch is engaged. Are you talking about the screw right on the switch plate or the other adjustment screw lower on that arm? I guess I don't quite understand this switch and how adjustments affect the idle.

Thanks

[sweetp01569]

I am confused what could have changed between one ride and the next where it was smooth and now fluctuates?

[Bitsyncmaster]

Thanks Dave. Are you talking about the microswitch screw? At idle the switch is engaged. Are you talking about the screw right on the switch plate or the other adjustment screw lower on that arm? I guess I don't quite understand this switch and how adjustments affect the idle.

Thanks

Set the screw that pushes the idle switch. You want it to close the switch a little sooner. So turn it clock wise about a half turn.