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IAC RPM Fluctuations

Introduction to Engine Tuning

Discussion and questions related to the course Introduction to Engine Tuning


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Hello, I’m running a microsquirt on an s13 sr20det, id1000, gtx3582r, hks 264 cams, and a ford pwm idle valve.

i have a question in regards to the idle valve and setting it up. I had issues with my oem Nissan idle valve so I switched to a ford valve which runs pretty well on a megasquirt system.

The way I set it up was to completely close the throttle body with the stop screw and let the iac do all the air bypass. I feel as though this is wrong because I will occasionally get 2500rpm +/- 500 isles while the car is sitting at 1000rpm idle, without any throttle applied. Data logs show no change in valve pwm, afr seem to be within 5% error at 1000 and 2500rpm.Should I open the butterfly to get me in the ballpark of 800-900 rpm and then let the idle valve do the rest of the fine tuning? Or am I setting this up correctly.

thanks.

Hello i recommend setting the the throttle plate close to the desired rpm when hot and no aux things turned on

then using the idle speed valve to control around this when needed like ac power steering fans etc

Regards Ross