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.
Less than −60.0 kPa (−450 mmHg, −17.72 inHg)
Diagnosis of engine condition by measurement
of intake manifold vacuum
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Vacuum
gauge indication
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Possible
engine condition
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1. Needle
is steady but lower than normal position. This tendency becomes
more evident as engine temperature rises.
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Air leakage
around intake manifold gasket, disconnection or damage of vacuum
hose
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2. When
engine speed is reduced slowly from higher speed, needle stops temporarily
when it is lowering or becomes steady above normal position.
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Exhaust
pressure is too high, or exhaust system is clogged.
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3. Needle
intermittently drops to position lower than normal position.
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Leakage
around cylinder
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4. Needle
drops suddenly and intermittently from normal position.
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Valve anchoring
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5. When
engine speed is gradually increased, needle begins to vibrate rapidly
at certain speed, and then vibration increases as engine speed increases.
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Weak or
broken valve springs
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6. Needle
vibrates above and below normal position in narrow range.
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Defective
ignition system
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