Idle Control System; System Description - Acura 3.5 RL Manual

Idle Control System

System Description

The idle speed of the engine is controlled by the Idle Air Control (IAC) Valve.
The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled by the
PCM. When the IAC Valve is activated, the valve opens to maintain the proper idle speed.
1. After the engine starts, the IAC valve opens for a certain time. The amount of air is increased to raise the idle speed
about 150 - 300 rpm.
2. When the coolant temperature is low, the IAC valve is opened to obtain the proper fast idle speed. The amount of
bypassed air is thus controlled in relation to the engine coolant temperature.
3. When the idle speed is out of specification and the scan tool does not indicate Diagnostic Trouble Code (DTC) P0505 or
P1508, check the following items:
• Adjust the idle speed (see page 11-124)
• Air conditioning signal (see page 11-116)
• ALT FR signal (see page 11-118)
• Starter switch signal (see page 11-119)
• Transmission range signal (see
• PSP switch signal (see page 11-120)
• Brake pedal position switch signal (see page 11-122)
• Idle air control thermal valve (see page 11-123)
• Hoses and connections
• IAC valve and its mounting O-rings
4. If the above items are normal, substitute a known-good IAC valve and readjust the idle speed (see page 11-124).
If the idle speed still cannot be adjusted to specification (and the scan tool does not indicate DTC P0505 or P1508) after
IAC valve replacement, substitute a known-good PCM and recheck (see page
symptom goes away, replace the original PCM.
IDLE
AIR
CONTROL
THERMAL
VALVE
INTAKE
MANIFOLD
section 14)
ENGINE COOLANT
IAC VALVE
IDLE
ADJUSTING
SCREW
11-42 for immobilizer information). If
From
PGM-FI
MAIN
RELAY
VARIOUS
SENSORS