[Lorenfb]

"The AAV is a vacuum-operated valve working in conjunction with the AAR."

All three valves (AAR, AAV, DECEL) provide parallel vacuum sources
bypassing the throttle butterfly:

1. The AAR's function controls fast idle during warmup, i.e. a steady-state
idle affected by engine temp and time.
Problems:
a. Low idle at cold start - valve stuck (closed)
b. High idle at warm engine - valve stuck (open), or no 12 volts
2. The AAV's function provides additional air during starting (zero/low vacuum),
i.e. both cold & warm starting, causing a momentary fast idle.
Problems:
a. High idle - valve stuck (open)
b. No momentary fast idle at startup - valve stuck (closed)
3. The DECL's function is to control the rate of change of RPMs to prevent
idle undershoot and to reduce emissions (HCs) during decel.
Problems:
a. High idle - valve stuck (open)
b. Idle undershoot or engine dies on decel - no small vacuum line, stuck valve (closed)