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Old 12-30-2020, 02:11 PM   #1
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Join Date: Nov 2017
Location: Sacramento
Default Microsquirt PWM idle valve wiring

Hey y’all,

So here’s my weird question... When wiring a Volvo 940 Bosch 2-wire IAC to a microsquirt, does one need to include a 1N4001 diode in order to get things to respond in a normal fashion? Ive tried three different IAC’s out of the car and they all respond the same. When using the IAC test mode output in tunerstudio they clatter around and only open from the values 80-95% intermittently...makes tuning WUE on a cold start a real pain. Anyone got any experience with microsquirt and idle valve wiring?

Any input would be awesome, Cheers!
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Old 12-30-2020, 09:26 PM   #2
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solution found! Microsquirt requires a diode (1n4001) to be soldered into the two wires with the banded side to the 12 signal wire. The pwm 2 wire valve now works as it should and cold start tuning is possible!
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Old 12-31-2020, 02:35 AM   #3
Ronald Culberbone III
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Gotta like the "recommended" diode on page 32. I bet this is the reason I could never get the IAC to behave properly.

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Old 01-06-2021, 09:18 AM   #4
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Location: mont, AL

yeah it needs that. I've gotten them to work without it, but they work a lot better with it.
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Old 01-06-2021, 09:32 AM   #5
I.M. Weasel
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Join Date: Sep 2011
Location: Driving the No Malarkey Bus

I gave up and plumbed the k- jet thermo valve in. It doesn't seem to work either though, maybe I need to try another one.
Living life one day at a time. Stopping to smell the oil slick beneath my Volvos.
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Old 01-10-2021, 09:23 AM   #6
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Join Date: Jan 2009
Location: Fate, Tx

1n4001 diode. Freq 100-120, duty about 25min 60 max. Use open loop to find the min/max and then set your closed loop accordingly. Make sure to use idle initial value x CLT and idle spark advance as well to help control surges.
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Old 01-10-2021, 03:54 PM   #7
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Diode lives easy happy life in connectors rubber boot.
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