IAC Problem: Idle too high until restart

For discussing injector selection,manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
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jmoney454
MegaSquirt Newbie
Posts: 2
Joined: Sat Sep 13, 2008 1:43 pm

IAC Problem: Idle too high until restart

Post by jmoney454 »

MS-II V3.0 I have a problem with the IAC. It seems to stop responding to commands before the car is fully warmed up, leaving the idle too high. According to the MegaManual (http://www.megamanual.com/ms2/IAC.htm), there is a possible fix involving jumpering two resistors labeled 1R0. I can't seem to find these at all, maybe they're from the 2.2 board?

The MegaManual says "This is very likely to be the problem for those who see the proper step commands given in software but inconsistent response from the motor, such as requiring a restart to lower the hot rpm after a cold start." This exactly describes my problem, but I can't figure out what to jumper. Anyone with a V3.0 have any luck figuring out how to do this mod?
BottleFed70
MegaSquirt Newbie
Posts: 31
Joined: Fri Jun 24, 2005 2:22 pm

Re: IAC Problem: Idle too high until restart

Post by BottleFed70 »

What version of the firmware do you have?

Older versions of the firmware have a bug that will produce the exact same problem that you describe.
1970 Ford Mustang
351W Single T70 Turbo 6 PSI
MSII, v3.0 PCB, v2.889 firmware, Megatune 2.25
jmoney454
MegaSquirt Newbie
Posts: 2
Joined: Sat Sep 13, 2008 1:43 pm

Re: IAC Problem: Idle too high until restart

Post by jmoney454 »

Thanks for the advice, I think I finally figured it out. I had a bad IAC, I replaced it and everything seems good now.
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