Does Idle Air Control Valve Work As A PWM or Fast Idle valve?
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MBWorld Fanatic!
Joined: Feb 2007
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From: Connecticut, New Haven
95' AMG SeeThreeSix
Does Idle Air Control Valve Work As A PWM or Fast Idle valve?
I'm currently building the Megasquirt II v3.0 ECU, planning to go full EFI and EDIS ignition. The Idle air control valve circuit allows for either Stepper, Pulse Width Modulation, or just fast idle (on/off) operation. I need to know if the stock setup controls the IAC valve by PWM slowly adjusting the air until the coolant temp is sufficient, or just on/off until it hits the coolant temp threshold. Can anyone confirm either or? Thanks guys, I plan to do a whole detailed writeup on my Megasquirt install for the forum, but not anytime soon its going to be a "piece together" project as funds are tight for the time being. 
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From: REHOBOTH BEACH DE
88-300CE TWIN TURBO, 99-C43, 05-G55K, 71-280SL, 94-E320 CAB, 08 CLK63 BLACK SERIES
I'm currently building the Megasquirt II v3.0 ECU, planning to go full EFI and EDIS ignition. The Idle air control valve circuit allows for either Stepper, Pulse Width Modulation, or just fast idle (on/off) operation. I need to know if the stock setup controls the IAC valve by PWM slowly adjusting the air until the coolant temp is sufficient, or just on/off until it hits the coolant temp threshold. Can anyone confirm either or? Thanks guys, I plan to do a whole detailed writeup on my Megasquirt install for the forum, but not anytime soon its going to be a "piece together" project as funds are tight for the time being.
Later models used a rotary deviced controlled by the ECU and functioned not only during cold start and warm up, but under load ( AC, PS actuation ) to stabilize and control idle ( PWM ???? ).
Last edited by RBYCC; Dec 16, 2008 at 09:30 AM.
Thread Starter
MBWorld Fanatic!
Joined: Feb 2007
Posts: 1,297
Likes: 1
From: Connecticut, New Haven
95' AMG SeeThreeSix
You have a 1986 M103-12V which probably has an air bypass valve around the throttle valve during cold start and warmup. Control is by an internal bi-metal strip ( on-off ).
Later models used a rotary deviced controlled by the ECU and functioned not only during cold start and warm up, but under load ( AC, PS actuation ) to stabilize and control idle ( PWM ???? ).
Later models used a rotary deviced controlled by the ECU and functioned not only during cold start and warm up, but under load ( AC, PS actuation ) to stabilize and control idle ( PWM ???? ).
Looks like I'll be off to the scrapper later this week for a nice PWM IAC/bypass valve. I want a completely reliable MS setup year round, so for cold days this is a must!
