When should I smoke test my car?

In the first of our Question of the Week videos, we tackle the issue of smoke testing your car, what that means, how to do it, and when you should.

One of the most common issues that can come up on a tuned Subaru, or a turbocharged Subaru as it ages is a vacuum leak. If there is a hose that has come lose, or cracked, or is not sealing completely, you can end up letting air in that isn't metered by your mass-airflow sensor, and that can cause various different drivability issues. The most common of these are not being able to hit your target boost pressure, rough or stumbling idle, or a lean running condition.

Tracking down this kind of issue can be tricky, but using a smoke machine to send slightly pressurized smoke through the intake path of your car is a great way to test for and find leaks. This is a very handy diagnostic test even on a car that doesn't have any obvious issues. It would always be a good idea to smoke test your car before you head to the track, or especially before you put the car on a dyno to be tuned just to make sure that everything is sealed up properly and working as it should.