Checking For Restriction

INSPECTION (ON-VEHICLE)
1. Start the engine and verify that there is no exhaust gas leakage from the exhaust system components.
2. If an exhaust leak is found, replace parts as necessary.
3. Connect a vacuum gauge to the intake manifold vacuum source.
4. Connect a tachometer to the engine.
5. Start the engine and place the transmission into neutral.
6. Gradually increase the engine speed to 2000 rpm while observing the vacuum gauge.
7. Decrease the engine speed to idle while observing the vacuum gauge.

NOTE: The vacuum gauge reading may be normal when the engine is first started and idled. However, excessive restriction in the exhaust system will cause the vacuum gauge to drop to a low point even while the engine is idled.

8. The manifold vacuum should exceed 53 kPa (16 in. Hg).
9. If the manifold vacuum exceeds specified vacuum, then the exhaust system is OK.
10. If the manifold vacuum does not exceed specified vacuum or the vacuum is slow to return to normal, then inspect the following components for restrictions:
^ Silencer
^ Three-way catalytic converter
^ Exhaust manifold(s)