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ME(H4DOSTC)-24 MECHANICAL INTAKE MANIFOLD VACUUM 5. Intake Manifold Vacuum A: INSPECTION 1) Warm-up the engine. By observing the gauge needle movement, the in- Vacuum pressure (at idling, A/C “OFF”): Less than −−−− 64.0 kPa ( −−−− 480 mmHg, −−−− 18.90 inHg) ME-00008 Diagnosis of engine condition by measurement of manifold vacuum Vacuum gauge indication Possible engine condition 1. Needle is steady but lower than normal position. This ten- Leakage around intake manifold gasket or disconnection or 2. When engine speed is reduced slowly from higher speed, Back pressure too high, or exhaust system clogged 3. Needle intermittently drops to position lower than normal Leakage around cylinder 4. Needle drops suddenly and intermittently from normal posi- Sticky valves 5. When engine speed is gradually increased, needle begins to Weak or broken valve springs 6. Needle vibrates above and below normal position in narrow Defective ignition system or throttle chamber idle adjustment. |