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100-04-24 Noise, Vibration and Harshness 100-04-24 DIAGNOSIS AND TESTING (Continued) Condition Source Action Excessive runout of valve seats on the CARRY OUT a valve seat runout test. INSPECT the valve face and seat. valve face. INSTALL new valves as necessary. Rattling noise—from the bottom of the Loose muffler shields or catalytic CHECK the exhaust system for loose vehicle converter shields. shields. REPAIR as necessary. Thumping noise—from the bottom of Exhaust pipe/muffler grounded to CHECK the exhaust system to chassis clearance. CHECK the exhaust system the vehicle, worse at acceleration chassis. hangers for damage. REPAIR as Engine vibration—increases intensity CARRY OUT Neutral Engine Run-up Engine out-of-balance. (NERU) Test. ROTATE the torque as engine rpm is increased converter, 120 ° for 3 bolt and 180° for 4 bolt. INSPECT the torque converter Engine vibration—is felt with increases CARRY OUT the Exhaust System Strain on exhaust mounts. Neutralizing procedure in this section. and decreases in engine rpm REPAIR as necessary. Damaged or worn powertrain/drivetrain CHECK the powertrain/drivetrain mounts for damage. REPAIR as mounts. necessary. Engine or transmission grounded to INSPECT the powertrain/drivetrain for correct clearances. REPAIR as chassis. necessary. Engine vibration—vibration felt at all CARRY OUT Engine Accessory Test. Excessive engine pulley runout. INSTALL a new engine pulley as times necessary. REFER to Section 303. Damaged or worn accessory CARRY OUT Engine Accessory Test. REPAIR or INSTALL a new component. component as necessary. REFER to Engine vibration—mostly at CHECK the ignition system. INSTALL Combustion instability. coast/neutral coast—condition new components as necessary. improves with vehicle accelerating Engine vibration or shudder—occurs INSPECT the spark plugs for cracks, Worn or damaged spark plugs. with light to medium acceleration high resistance or broken insulator. above 56 km/h (35 mph) necessary. REPAIR or INSTALL a new injector as Plugged fuel injector. necessary. INSPECT the spark plug wires for Damaged spark plug wire. damage. INSTALL a new spark plug INSPECT the fuel for contamination. Contaminated fuel. DRAIN the fuel system and refill. CHECK the torque converter. INSTALL Worn or damaged torque converter. a new torque converter as necessary. Symptom Chart—Idle Noise/Vibration Condition Source Action Idle air control (IAC) valve moan — GO to Component Tests in this IAC valve is contaminated with oil. occurs on throttle tip-out section. G72679 en |