Air injection systems send clean air into the exhaust system to encourage the complete burning of fuel in exhaust gases. To accomplish this task, rubber, synthetic, or metallic lines are used to transport air from the air filter box or throttle body inlet to the air injection pump, then from the air injection pump into the exhaust or intake manifold, depending on the state of the control valve.

The lines between the exhaust manifold and air injection pump are typically metallic, and this prevents them from damage due to excessive heat. However, the other lines for the system are likely to be rubber, plastic or synthetic, as these lines are only subjected to minor heat and light pressures.

Leaks in the air injection system lines are likely to cause no issues unless they occur between the check valve and the exhaust manifold, or the bypass valve and the intake manifold. In these two situations, the vehicle would likely run slightly rough, and may hesitate on acceleration. If the check engine light does come on, the codes will likely be for the catalytic converter, oxygen sensor, air to fuel ratio, or air injection system. A small leak is not likely to be detected. If the leak becomes large, you may notice the engine attempting to stall at idle, or any time the throttle is not applied.