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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.