The First Device is a Cold Start Idle Speed Adjustment. It will be naturally open a little ( its a rotating Disk ) and when the fuel pump Power ( orange wire ) gets powered up, it will heat a Bi-Metal Strip that will slowly close the disk.. Its like the Old Electric Choke Controls on the 70s cars.
If you disconnect the power to it after its running, it will likely take ~1 hour for it to fully close.. The Cold Start Idle Up Device supplies it's air through the ~1/2 inch rubber hose hooked through the center of the balance tube.The Second Device is the 'Idle Up Solenoid' that will open a predetermined amount when powered, to cause the engine not to stumble when the AC Compressor is kicked in.. The Third and last device id the Idle Air Control Valve. Its a stepper control device that will do the final adjustment of the engine speed by the ecu. The First Device is ONLY used to idle up till warm. The Second Device is only used for the AC. The Third Device is the only device needed for operation. If you Plug the 1/2 Hose at the Crossover Tube, it will keep the Cold Start Idle From Working, however the Third device has the idle speed range to make up for the Cold Start.. Removal of the First two devices is a Common thing to simplify the Idle Circuit and plugs on the back of the Z32 Intake. However, it may not be done in California, as that is modifying the intake system and it will fail the Visual Inspection part.. I have done the Bypass on the 1/2 inch hose, and I like my Cold and warm start idle speed better now.. As for your Over Under Idle Speed.. Is it the Carbon Canister Unloading Vapor?.. Cj
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