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INSPECTION

INSPECTION

Idle the engine.

Disconnect the brake vacuum hose from the intake manifold, and then install the vacuum gauge.

Keep the engine at the idle speed and read the vacuum gauge indication.

By observing the gauge needle movement, the internal condition of the engine can be diagnosed as described below.


Vacuum pressure (at idling, A/C “OFF”):

Less than −60.0 kPa (−450 mmHg, −17.72 inHg)

Diagnosis of engine condition by measurement of intake manifold vacuum

Vacuum gauge indication

Possible engine condition

1. Needle is steady but lower than normal position. This tendency becomes more evident as engine temperature rises.

Air leakage around intake manifold gasket, disconnection or damage of vacuum hose

2. When engine speed is reduced slowly from higher speed, needle stops temporarily when it is lowering or becomes steady above normal position.

Exhaust pressure is too high, or exhaust system is clogged.

3. Needle intermittently drops to position lower than normal position.

Leakage around cylinder

4. Needle drops suddenly and intermittently from normal position.

Valve anchoring

5. When engine speed is gradually increased, needle begins to vibrate rapidly at certain speed, and then vibration increases as engine speed increases.

Weak or broken valve springs

6. Needle vibrates above and below normal position in narrow range.

Defective ignition system