Awesome video. A lot of people tell me the IAC valve is either fully open or fully closed. But some mention it is a stepper motor but nobody seems to know exactly what the IAC is doing. When you talk about Pulse Width Modulation (PWM) I know what that means I am an engineer, so you are saying the IAC is fully opening and closing at different ratios (duty cycle) to get an over all air flow of Zero to Max, or is it an actual stepper motor. If it is a stepper motor, you simply give it pulses in one director or the other to put the IAC plunger right where you want it. In your video you were talking about it being controlled by PWM duty cycle but in some cases you mentioned steps alluding it to being a stepper motor. This has been very confusing because a lot of people have the concept, but gloss right past the details. You seem to have the deeper dive into knowledge that I seek. I have an IAC for a 1987 GM V6 2.8L Multi-Port fuel injection Pontiac Fiero. It has only 4 pins. One pair reads 50 Ohms across it, and the other pair reads 50 Ohms as well. I am guessing one pair is a coil that steps the plunger out a tiny bit for each pulse, and the other pair steps the plunger in a tiny step for each pulse. I can move the plunger in and out by hand, it feels like it is geared down inside, so I guess it must be a motor (but is it an actual STEPPER motor)? My experience with linear stepper motors (in/out rather than round and round) is, you send it many pulses more than is needed to get it to one of its stops - home position. Then you can change the position of the plunger by the number of in/out pulses (steps) you apply it (not PWM, actual step pulses). Say it takes 255 steps to open it fully, you send it 256 steps (pulses) in the open direction - this guarantees the pluger is fully open no matter where it was when power is off - it is now in the home 100% position. If I wanted to move it to the 50% position, I would send it 128 pulses in a row stepping it toward closed. And the plunger stays right there - it doesn't move. Then to move it to the 75% position, I pulse it 64 steps in the other direction toward open. The nice thing about stepper motors is, when you step them to any position, they stay in that position without any power (pulses) and they are very accurate because you keep track of the pulses you sent it to know its position. But if it is a PWM duty cycle plunger, then I cant see how a smooth idle can obtained with it fully opening and fully closing at some fast rate duty cycle. Any idea on how I can actuate my IAC valve to learn exactly how it works? One would think there would be at least one more pin to give position feedback to the ECM just to be sure. Thanks.
hey andy, something you just mentioned just got me thinking. so when i set my ITB alpha N motor up, should i calibrate my TPS to 0 after setting up my itbs to idle, or should i first reset it to 0 with throttle blades fully shut and then manually adjust the throttle adjustment screw such that my TPS sensor reads (some value, lets suppose 5%) with no throttle input from my foot. if you get what i mean.
I'm confused... After watching this video like 10 times, the section from 5:30 to 5:43 confused me. You disconnect the IAC, then set the throttle blade to an RPM lower than the idle target, then plug the IAC back in and set to 30%, then adjust the throttle blade to your target idle RPM? If the IAC is set to 30% and creating a high idle, how would you get the idle down to your target? Wouldn't the IAC be introducing air and keep the idle high? 🤔
