7.4 Startup / Idle 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
7.4.4.3 PWM idle valve settings
• Crank-to-Run Taper Time - This is the amount of time the IAC valve uses to transition after starting from its
crank position to its running position.
• Valve Mode - Normal mode is off at 0% duty cycle, inverted mode is off at 100% duty cycle. As the name im-
plies, most valves use normal mode. If you’ve found you accidentally wired up a 3 wire IAC valve backwards,
just flip this setting.
• Run valve before start - If set to on, the valve is energized with the key on and engine off. This allows for
slightly faster starting, but some PWM valves may make an objectionable amount of noise before starting.
Turning this off will prevent the valve from making noise with the engine off, but may produce a small delay
in starting.
• Output Port - Allows you to pick which output wires are used. In 3 wire mode, this is for the coil that opens
the valve.
• 3 wire mode - Used with 3 wire rotary IAC valves, common in Denso and Bosch applications. This may be
left off or used to specify the connection used for the coil that closes the valves.
• Valve Frequency Selection - Select a frequency from the list. Different valves operate best on different
frequencies.
7.4.5 Idle Cranking Duty / Steps
This screen gives how much IAC valve opening to apply when the engine is cranking as a function of temper-
ature. A larger value means more opening. PWM valves go from zero to 100% duty, while stepper valves allow
specifying how many steps to use.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 183
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