DIY_EFI Digest V4 #592

[Al Jurenas]

| From what I can tell, the ECM (on a 90 GM) keeps track of the IAC position
by remembering how many pulses it has sent out. This count shows up on a
scanner.

I believe the ECM reseats the IAC pindle (sends out multiple pulses to bring
it all the way in or out) every time:
(a) The battery power is removed and reapplied     (b) you put the ECM in
diagnostic mode by grounding at the ALDL connector, and
(c) The car is driven at over 20 mph.
By doing this, the ECM knows what position the IAC is, and recalibrates the
IAC position by resetting the pulse count.


| Date: Wed, 20 Oct 1999 13:32:04 +0100
| From: Ade + Lamb Chop <alaw at mrc.soton.ac.uk>
| Subject: Re: DIY_EFI Digest V4 #590
|
| At 15:00 19/10/99 -0400, DIY_EFI Digest wrote:
| >
| >Date: Tue, 19 Oct 1999 07:53:07 PDT
| >From: "Gary Moulton" <gmoabrim at hotmail.com>
| >Subject: Manual control of IAC motor
| >
| >Can someone tell me which terminals of the IAC motor runs the pintle in
and
| >out? The wiring diagrams show two coils and the connector has 4
terminals.
| >Does one coil send the position back to the ecm and the other is a 12
volt
| >reversable dc motor?
| >
| >Application is 1994 Mopar 4.0L EFI in a 1982 Jeep CJ-7, and what I want
to
| >do is be able to manually adjust the idle lower than the 750-800 rpm when
| >off-roading. I have connectors and a harness and some electrical
experience.
| >I plan to have a switch to disconnect the IAC from the system for manual
| >control and a spring loaded switch to "bump" the IAC position in or out.
| >There is a company offering such a controller for more money than I think
it
| >should cost to build one myself. Thanks in advance
|
| I don't know about your system but the mini one IAC is a stepper motor.
You
| need a driver to run it. The motors I have seen have a permanant magnet on
| the spindle then the driver powers coils to step the field round. I am
| supprised it doesn't have any feed back of where it is though. I suppose
| the ECU gets it to the right place by trial and error. Then resets it's
| self back to a postion where startup is good.
|
| There are loads of driver chips around cannot think of on off hand. There
| are 2 different sorts of motor too 4 and 6 wire ones... cannot remember
| what yours is called tho.
|
| HTH,
|
| Ade
|
|