Air regulator:

One of the mechanical problems that cropped up with the Z was a rough to dying idle when starting the car cold. Thanks to the people at 300ZXClub, it was determined that my air regulator was bad, so I ordered a new one from NissanParts.cc. The part number was 22660-V5015. Before I ordered a new regulator, I did a quick test that was also suggested on the 3ZC forums. If you place the air regulator in a freezer for half an hour or so, and look into it, the hole should be completely open. The reason it works like that is so air can bypass the normal routes to warm the engine up. As the engine warms up, the valve in the air regulator will slowly close until the engine is fully warm. Here's what mine looked like after half an hour in the freezer - almost no movement.