INSPECTION
INSPECTION |
Warm-up the engine.
Disconnect the brake vacuum hose, and then install the vacuum gauge to hose fitting on manifold.
Keep the engine at the idle speed, and then read the vacuum gauge indication.
By observing the gauge needle movement, the internal condition of 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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Leakage
around intake manifold gasket or disconnection or damaged 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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Back pressure
too high, or exhaust system 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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Sticky
valves
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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 or throttle chamber idle adjustment
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