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Idle issues when A/C turns on Subaru V7


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Hi guys, 

Having a few issues with unstable idle when the A/C Clutch and Fan kick in. It seems like the idle up tables don't do much and the car nearly stalls but then recovers and runs ok with the A/C running. When the A/C turns off the idle drops a bit and settles then the process happens again once the A/C turns back on. 

Car is in closed loop idle control, the idle is set to 700rpm idle base position is set to 20%.  I have tried turning Closed loop off also and didn't notice a great deal of difference. 

Any ideas? I grabbed the logs but I'm not really sure on how to read them..


ECU Log 2019-12-24 9;24;49 pm.llg

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Cant see on your log since it doesn't include everything, but I have a few suggestions:

- Have a look to see what your fuel trim is doing when the AC compressor kicks in. I know there is a trim that can increase fuel PW in response to the compressor getting commanded on. If it is coming on, it might make the engine a little unhappy, depending on how large the trim is. It's Under the Idle Load Trims. You are looking for AC Trim. Ensure it is zeroed out, and see if that helps.

- Alternatively, you could set up your fan control if you have not already to ensure that only one fan comes on at a time (staggered), thus, ensuring that the current draw of 2 fans coming on at the same time doesn't upset the engine too much.

- Alternatively, under idle speed control, you can adjust "engine fan step" in order to keep the RPM a bit higher when the fans are running. That way the electrical load of the fans does not cause the engine to die.

- Adjust AC Step as well to give a bit more air to the engine when the compressor is getting commanded on.

- Alternatively, perhaps the gain of your closed loop idle control is not high enough?. 


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