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IAC capacitor fix...where?

Posted: Thu Aug 27, 2009 2:47 pm
by phongshader
I've been struggling for years to get the iac to work consistently. I started out with this unit in the DarkStar housing:
http://shop.oreillyauto.com/productdeta ... 06&PTSet=A
and jumping the 2 resistors io the msII board
It would start fine but would idle too fast when warmed up until the engine was restarted then it idled fine. After trying many different settings , from time, minumum step. start position, and son on I could never get it to work correctly so I tried a different valve:
http://www.napaonline.com/MasterPages/N ... trol+Valve
which at 1st seemed to work as advertised, would start fine and then settle down to a reasonable idle when warmed up. However if I started and stopped several times within 5 or so minutes it acted like it lost synch with where it was and the idle would shoot up and would not close until the engine cooled down or wouldn't close at all and it did this inconsistenly...some days it worked great and other days not at all?!? So now I'm looking at adding a capacitor between the +12 V line to the stepper chip and ground, out lined here: http://www.megamanual.com/ms2/IAC.htm, to see if it will make the operation a little more consistent. Where do I solder the cap on the msII board? Where is there a schematic or picture of where to solder this? Actually a picture would be better as I probably wouldn't know where on the board the schematic is pointing to.

Re: IAC capacitor fix...where?

Posted: Sat Aug 29, 2009 7:51 pm
by phongshader
Really? No one can tell me where on the MSII board to solder a capacitor between the +12 V line to the stepper chip and ground?

Re: IAC capacitor fix...where?

Posted: Sun Aug 30, 2009 7:44 am
by grippo
From the manual it says: The most practical place is at the 40 pin socket where you put the +12V supply. Find the 12V and ground pins on the 40 pin socket, from the schematic, and solder a cap between these pins, probably on the bottom is easiest.

Re: IAC capacitor fix...where?

Posted: Thu Sep 03, 2009 11:33 am
by phongshader
So would I replace the 0.1 cap, c13 in schematic, with a 100 µF/25V? Or do I add one somewhere else or in addition to?

Re: IAC capacitor fix...where?

Posted: Sat Sep 05, 2009 4:23 pm
by grippo
Add one in parallel.