Originally posted by Tired2
So, there are two (well more like 4 or so) types of IAC out there. The stock one, at least on my '97 420A is a 4 wire stepper based IAC. To run it, you'll need to jumper in a few wires in the MS2 unless that has already been done. See the assembly guide, or contact the place you bought your MS from to see if you have support for it. The other common type is a PWM one, that yes, will go on the FIDLE output. I'm seem to recall that the FIDLE needs a TIP120 on it because the transistor does not have enough umph to get it done. You'll have to read up on the assembly guide to figure that out though, I can't recall. Or, watch my first 6 videos or so, I think I talk about FIDLE back when I thought mine was a PWM single wire one. The Symtechlabs 420A wiring diagram should get you close if you have a 4 wire IAC. ... The top left 4 wires that say IAC2B, etc. I don't have the wire colors handy, but it is easy enough to just ohm them out to find out which two pairs make a coil. Then, just use the test mode from my IAC video "IAC Physical Test" to make sure you have good movement. The Throttle body is easy to pull off... 5 minutes or so. I broke an IAC bolt trying to get it out, so just pull the TB and look inside.

What did you have your Idle Control Setting too? The base map for 420a is on/off.. did you do PWM warmup? Stepper Closed, open??