- Idle air control (IAC) valve moan - occurs on throttle tip-out
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- IAC valve is contaminated with oil
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- Accessory drive belt chirp - occurs at idle or high idle, cold or hot. Most common occurrence is during humid weather
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- Accessory drive belt worn, or pulley is misaligned or loose
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- INSPECT for loose or misaligned pulleys. CHECK the drive belt for wear or damage. INSTALL new pulley(s)/drive belt, as necessary. REFER to ACCESSORY DRIVE
.
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- Accessory drive bearing hoot - occurs at idle or high idle in cold temperatures of approximately +4°C (+40°F) or colder at first start of the day
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- Accessory drive idler or tensioner pulley bearing is experiencing stick/slip between ball bearings and bearing race
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- Power steering moan - occurs at high idle and possibly at idle during the first cold start of the day in temperatures of approximately -18°C (0°F) or colder. Noise can even be a severe screech for less than one minute in very cold temperatures of approximately -29°C (-20°F) or colder
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- High fluid viscosity, or plugged reservoir screen in power steering reservoir starves pump causing cavitation
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- Generator whine - during high electrical loads at idle or high idle, a high pitch whine or moan is emitted from the generator
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- Generator electrical field noise
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- Using an EngineEAR, PROBE near the generator housing. LISTEN for changes in the noise level while changing electrical loads (such as rear defrost, headlamps, etc.). CARRY OUT a generator load test. Refer to CHARGING SYSTEM - GENERAL INFORMATION
. If the system passes the load test, the noise is from the generator bearings, INSTALL new bearings. If the system fails the load test, INSTALL a new generator. REFER to GENERATOR AND REGULATOR
.
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- Engine-driven cooling fan moan - occurs during the first start of the day. It is most objectionable near idle speeds up to 2,000 rpm. The noise increases with rpm
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- The viscous cooling fan clutch engages until the fluid in the clutch reaches normal operating temperature, causing the fan to fully engage
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- Drumming noise - occurs inside the vehicle during idle or high idle, hot or cold. Very low-frequency drumming is very rpm dependent
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- Exhaust system vibration excites the body resonances inducing interior noise
- Engine vibration excites the body resonances inducing interior noise
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- Hissing noise - occurs during idle or high idle that is apparent with the hood open
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- Vacuum leak or idle air control (IAC) valve flow noise
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- Use the Ultrasonic Leak Detector/EngineEAR to locate the source. SCAN the air intake system from the inlet to each cylinder intake port. DISCARD the leaking parts, and INSTALL a new component.
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- Vehicles with a plastic intake manifold
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- Acceptable condition. Some plastic manifolds exhibit this noise, which is the effect of the plastic manifold.
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- Automatic transmission buzz or hiss
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- Incorrect driveline angles
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- Worn or damaged main control solenoids or valves
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- Manual Transmission Clutch throw-out bearing whine. A change in noise pitch or loudness while depressing the clutch pedal
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- INSTALL a new throw-out bearing.
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- Heating, vacuum and air conditioning (HVAC) system chirp - most audible inside the vehicle. Listen for a change in noise pitch or loudness while changing the HVAC system blower speed
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- Damaged or worn HVAC blower bearing
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- Air conditioning (A/C) clutch ticking - occurs when the compressor clutch engages
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- Acceptable noise
- Incorrect air gap
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- LISTEN to the clutch to determine if the noise occurs with clutch engagement. A small amount of noise is acceptable. If the noise is excessive, CHECK the A/C clutch air gap. INSPECT the A/C clutch for wear or damage. INSTALL a new clutch as necessary. REFER to CLIMATE CONTROL
.
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- Intermittent rattle, or scraping/rubbing noise
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- Loose exhaust heat shield(s)
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- INSPECT the exhaust system for loose parts using a glove or clamps to verify cause. REPAIR as necessary. REFER to EXHAUST SYSTEM
.
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- Wiring, hose or other part interfering with accessory drive belt or pulley
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- INSPECT accessory drive system closely verifying there is adequate clearance to all rotating components. REPAIR as necessary.
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- Engine ticking or knocking noise - occurs during idle or high idle during the first cold start of the day
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- Piston noise or valvetrain noise (bled down lifter/lash adjuster)
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- A continuous, speed-dependent rattle from the engine - occurs during idle or high idle during the first cold start of the day and disappears as the engine warms up
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- Piston noise or valvetrain noise (bled down lifter/lash adjuster)
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- Idle vibration - a low-frequency vibration (5-20 Hz) or mild shake that is felt through the seat/floorpan
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- Engine or torque converter out of balance
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- VERIFY the torque converter to crankshaft pilot clearance is correct, REPAIR as necessary. RE-INDEX the torque converter on the flex plate by 120 degrees on a 3 bolt converter or 180 degrees for a 4 bolt converter. REFER to AUTOMATIC TRANSAXLE/TRANSMISSION
. RETEST the vehicle.
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- Idle vibration - a high-frequency vibration (20-80 Hz) or buzz, that is felt through the steering wheel or seat
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- Exhaust system mounts bound up
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- VERIFY concern occurs at engine firing frequency. CHECK that the exhaust system vibrates at the same frequency as the engine. ADD 9-14 km (20-30 lb.) to the tail pipe to test. CARRY OUT EXHAUST SYSTEM NEUTRALIZING .
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- INSPECT the body mounts. CARRY OUT a Neutral Engine Run-Up (NERU) Test. REPAIR as necessary.
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- Power steering lines grounded out
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- INSPECT that the power steering lines are not contacting the chassis or each other. REPAIR as necessary.
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