running lean '76 280z

[darom]

Zed, I removed and inspected the inside of the AAR after a few test runs. Before the installation, I did the bench testing of it with a 12V and adjusted the curtain to be closed when the coil warms up.  Since it can't block air 100 percent, there is still some residual air flow which contributes to 900-950 rpm idle. If I pinch the rubber hose for the AAR, the idle immediately drops to 800 rpm, and it remains steady. In both of my tests so far the idle RPM was the same.

[Zed Head]

If the AAR closes to the same spot consistently, but idle speed varies, then the problem is not in the AAR.  My AAR worked correctly, and idle speed was consistent after warm-up.  In the end, I was lucky enough to experience an engine with everything working correctly.  But I also went through the phase of looking for alternative solutions.

The factory parts will give consistent cold start and warm-up to a properly idling and performing engine, if they are working as they were meant to work.

 

[Yarb]

Feel like you are going to go down a rabbit hole here. Check your AAR and go from there as @Zed Head suggested. 

[darom]

I think I figured out the AAR issue on my car.

Yesterday I was bench testing one of my AARs and noticed that blowing air one way allows for more air to pass through vs the other inlet when the curtain is closed. I checked onine pictures of the AAR orientation in the engine bay of other 280z owners and realized that my AAR was/is installed backwards (the electric connector is facing the firewall). I am going to change it tonight after work and see if this improves the idle speed 🙂 If this is the case, I have had the AAR installed wrong way for at least 5 years now. And you know how it feels ...

[Yarb]

Not sure how much or any difference that would make. Have you checked it with power? The results will be the same whether its on or off the motor. Opening and closing properly. Most Ive found are ether frozen open or closed.

[darom]

With the correct AAR orientation, at the beginning the idle was at 1100 rpms, within 2.5 minutes I saw the idle speed slowly going down. Once the air regulator valve was completely closed (i could check it by pinching the AAR hose - it didn't affect the idle speed), I set the idle at 850 rpms. It is steady. I will check the car again in the morning to test, but I am positive the issue with high idle/AAR has been resolved.

Also I was able to shut the engine down by screwing the idle screw in. I couldn't do it before. I still need to redo my oil pan gasket to get 1-2 in of vacuum : - )

Big thanks to everyone on this forum.