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Old 09-10-2012, 07:06 PM   #1
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Default IAC valve not working

Hi there!

I have been pretty happy with my Megasquirt so far, had it for about six months now, got it tuned to perfection, and all is well with the world... Except for one small thing I never managed to fix: My Idle Control Valve does not work.

I have been suspicious of this since the beginning, seeing as I have fiddled around with the idle settings a bit but they didn't seem to reflect any change. I settled with the fact that would have to stabilize cold idle with my accelerator pedal, and I was fine with that for a few months.

But since I went back to tuning the ECU for some changes today, I figured since I was at it I might just check the IAC valve function. So I did. I disconnected the valve and proceeded to turn on the car. To my surprise it turned on roughly as it usually does and then stabilized around the 900 RPM.

I then proceeded to place the valve plug back in, and no noticeable change in idle.


So... I'm sure my valve was working because my car used to fast idle on the stock ECU. It never did with the Megasquirt. I'm using the stock 90-93 settings for the idle, so I'm placing the blame in the outputs or a hardware problem. What do you guys think it could be?

My outputs settings are as follows:






I'm not bothered by this problem because the car runs flawlessly now, except when started from cold. But I would appreciate having this fixed anyway.
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IAC valve not working-07312012_1.png   IAC valve not working-fastidleproblems.png  
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Old 09-11-2012, 10:26 AM   #2
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Exactly what MS variant do you have? I see it's MS1 based, but that can cover a lot of ground.
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Old 09-11-2012, 10:42 AM   #3
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Brain built MS1 with a plug and play harness, on a 90-93 miata
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Old 09-11-2012, 10:51 AM   #4
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was it a parallel harness? i havent built an MS1 in a few years.
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Old 09-11-2012, 10:53 AM   #5
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I have no idea what a paralell harness means... The harness is a DB25 to ECU loom converter basically, and the ECU is running standalone, and has inputs for wideband, VICS and knock (or so I'm told... It's also written in the harness).
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