Air is an essential component of keeping the engine properly functioning. However, too much air or not enough pressure can keep the engine from operating normally. There are a variety of vacuum lines that keep the engine operating. A leak in one of these hoses can cause problems.
One way to determine if there is a leak is by using smoke. Using a smoke test vacuum leak is a simple method. Over time, the materials composing the vacuum lines can deteriorate allowing leaks in the system to happen. To smoke out the leak, you need to plug one end of the hose leading to the intake manifold. Place the nozzle of the smoke machine on the manifold such as the brake booster line. Allow the smoke to filter through the hose for a few minutes. Look for signs of smoke throughout the engine. You can also use the system to find exhaust leaks.
It is a good idea to inspect the system for leaks before and after the smoke test. Small leaks can quickly add up to a large vacuum leak. If you replace the hoses, start at one end and methodically work your way around the engine until all hoses are replaced. This helps you keep your place and know which ones are new and which are old. Make sure all the hoses properly fit up against the various engine parts. Ill-fitting hoses can cause vacuum leaks.
Vacuum leaks however small can cause a decrease in the performance of your engine. The check engine light may pop on at the first sign of a leak. A vacuum leak allows the engine to take in too much air causing a reading error on the mass airflow sensor which causes the check engine light to come on. Too much air can cause the engine to idle roughly or even misfire. Finding and fixing the leak is a common issue for mechanics for all vehicles.