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IAC help needed.

Posted: Sun Jan 06, 2008 5:50 pm
by 64Vair
I hope this is the right place to post this. I have a 62 Corvair, which is, of course, air cooled. I have a MS2 v3.0 in it, and everything is great. Well, almost everything. I am having some issues with my IAC. I looked on the forum, and found some guy set his up for 160 steps to start. So I did that and it was TOO much! Car started great, but idled at almost 3 grand! So I pull it off, pull it closed, reinstall it, and set it to 50 steps. Started it and it was about perfect. I drive a little less than 1/2 mile to get gas, and shut the car off to fuel it. When I start it, it must have backed out another 50 steps because it was up around 2 grand plus!
Now my thing is, with an air cooled motor, I don't need ANY IAC over around 100 degrees F. When I had carbs on the car, with NO CHOKES, in mid 30 degree days, I would start the car, hold the accellerator for 10 seconds, back out of the drive, and by the time I drove 1/2 mile the car would idle on its own with no hint of stalling. I have been looking and cannot find a way to shut the IAC off fast. REally, once the car has been running 5 minutes, I no longer need it. In fact, I can run without it, just the first 1/2 mile it may want to stall at idle. I have the 2.883 firmware. Any ideas are welcomed!
Thanks guys, (and gals!)
Tom

Posted: Mon Jan 07, 2008 9:44 am
by grippo
I don't think you understand how this works. The starting value is for allowing the motor to run to the full open position from any position it happened to be in when the engine was shut off (this would generally be fully closed, but not always). Once the motor is fully opened, the processor knows where the motor is. At that point it immediately goes to the position specified in the IAC table as a function of coolant temperature. This doesn't have to be coolant, but it has to have some temperature reference, like cylinder head temperature. So you need to go back to 160 or whatever is right for your stepper motor, but then go into the steps vs temperature table and adjust it to suit what you need. If you don't need it above a certain temperature at startup, then you can make all the steps be closed for temperatures above this temperature.

Posted: Mon Jan 07, 2008 5:44 pm
by 64Vair
Ahh, I see the error of my ways! Thanks guys, much apprecaited!
Tom