280z Auxilary Air Regulator (AAR)
Purpose and Functioning:
The AAR is simply a "controlled leak" across the throttle body.
It simulates mildly reving the engine when it is first started (so-called fast idle).
The fast idle prevents the engine from bogging down and stalling while allowing
the engine to "warm up".
The AAR is designed to "close the leak" slowly over a few minutes.
It does this by a moving a stutter that closes off the air passage.
The shutter is pushed close by a bi-metal lever.
The bi-metal bends in one direction when it is heated. The heat is supplied
by a heater element at the base of the bi-metal level. Even if the heater
element fails, the bimetal will be heated by engine heat which is conducted
through the engine and manifold. Later engines had a cooling line run under the AAR.
Properly functioning AAR
Common Cause of AAR Failures:
Symptoms of AAR failure
Vacuum leaks, a faulty BCCD valve, stuck accelerator linkage, weak throttle
return spring or gummed open throttle body flap can also cause a fast idle.
Photos of a common AAR mechanical failure in which the bi-metal lever rotates out of position.
Cressida AAR variation that
can be relocated and mounted to bottom of TB
(note the output port on the bottom... this can feed directly into BCDD ports with proper matching plate)
(note 2. These AAR's have an additional pin that locks the bimetal to prevent it from rotating)