General Procedures - Engine Noise Diagnosis and Location

NVH symptoms must be identified using the diagnostic tools and methods that are available. For a list of these methods and tools, an explanation of their use, and a glossary of common terms,
For additional information, refer to: Noise, Vibration and Harshness (NVH) (100-04 Noise, Vibration and Harshness, Diagnosis and Testing).
Since it is possible that any one of several systems may be the cause of the symptom, it may be necessary to use an elimination-type diagnostic approach to accurately identify the responsible system.

Verify the customer concern by starting the engine to duplicate the condition.

Check the engine oil level and inspect the oil for contamination. Low engine oil level or contaminated oil are common causes of engine noise. If the oil is contaminated, the source of the contamination must be identified and corrected as necessary.

Visually inspect for obvious signs of mechanical damage.

If the inspection reveals obvious faults that can be easily identified, repair as necessary.

If the cause is not visually apparent, connect the diagnostic tool to the DLC.

If the diagnostic tool does not communicate with the VCM:

• Check the connection of the VCM to the vehicle.

• Check the connection of the diagnostic tool to the VCM.

• Check for no power to the scan tool to diagnose no power to the scan tool.
  For additional information, refer to: Communication Network (418-00 Module Communications Network, Diagnosis and Testing).

If the diagnostic tool does not communicate with the vehicle:

• Make sure the ignition switch is in the ON position.

• Check the operation of the scan tool on a known good vehicle.

• Diagnose no response from the PCM.
  For additional information, refer to: Communication Network (418-00 Module Communications Network, Diagnosis and Testing).

Perform the network test.

• If the scan tool responds with no communication for one or more modules,
  For additional information, refer to: Communication Network (418-00 Module Communications Network, Diagnosis and Testing).

• If the network test passes, retrieve and record the continuous memory DTCs.

Clear the continuous memory DTCs and perform a PCM self-test.

If the retrieved DTCs are related to the concern, go to the appropriate section 303-14.

If no DTCs related to the concern are retrieved, continue the inspection and verify whether the noise concern is related to the engine. For vibration and noise concerns such as transmission mount, air intake system and starter, GO to the NVH Symptom Chart.

Complete the following steps to locate the source of the engine noise. Compare the characteristics of the engine noise with those shown in the NVH chart.

1. Using a stethoscope, attempt to locate the source of the engine noise. Mark the location of any suspicious noises heard with the stethoscope.

   Click here to view engine noise diagnosis using a stethoscope.

   

2. If the noise is unclear using the stethoscope, attach the Chassis EAR at several locations on the engine. Attach the Chassis EAR to the suspected noise areas and to areas not suspected as the noise source for comparison. The Chassis EAR allows up to 6 clamps to be used to locate the source of the noise. Instead of or in addition to using the Chassis EAR, the EngineEAR can also be used. Wave or hold the EngineEAR over suspected areas of the engine to help determine the suspected noise.

   Click here to view engine noise diagnosis using the ChassisEAR.

   
   

   Click here to view engine noise diagnosis using the EngineEAR.

   

3. If the noise is still unclear using the stethoscope, ChassisEAR or EngineEAR, connect the scan tool. Use the VCMM oscilloscope function to view and graph the noise. Attach the VCMM accelerometers at the loudest suspected locations, as previously determined with the stethoscope, Chassis EAR or EngineEAR. Using the scan tool and VCMM accelerometers, graph the noise on the oscilloscope and determine whether the noise is upper or lower engine noise. For upper engine noise, place the accelerometers on both ends of the valve cover. For lower engine noise, place the accelerometers either at the end or from side to side of the engine block.

   Click here to view engine noise diagnosis using the VCMM and accelerometers.

   

4. If the noise remains unclear, or to verify the suspected noise from the stethoscope, ChassisEAR, EngineEAR or accelerometers graph, use a 3.5 mm male-to-female RCA adapter to connect the ChassisEAR or EngineEAR to the VCMM. Graph all or some of the noises, such as the accelerometers.

   Click here to view engine noise diagnosis using the VCMM and ChassisEAR.

   
   

   Click here to view engine noise diagnosis using the VCMM and EngineEAR.

   

5. If the location of the suspected noise still cannot be determined, use the VCMM oscilloscope function to graph any combination of accelerometer(s), ChassisEAR and/or EngineEAR to compare or identify the suspected noise. All 4 ports on the VCMM can be used to graph the noise.

   Click here to view engine noise diagnosis using the VCMM, ChassisEAR and accelerometer(s).

   
   

   Click here to view engine noise diagnosis using the VCMM, EngineEAR and accelerometer(s).

   

After localizing the noise, check the noise characteristics, including the type of noise, frequency, and the conditions under which the noise occurs. Use the NVH chart to determine the noise source.

NVH Chart

Symptom	Possible Source
Drone-type noise	Powertrain mount(s) Transmission
Drumming noise – occurs inside the vehicle at idle or high idle speed, when hot or cold. Very low-frequency drumming is highly dependent on engine speed.	Engine vibration excites body resonances, causing interior noise Transmission
Engine drumming noise accompanied by vibration	Powertrain mount(s)
Rattle	Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings Valvetrain
Chatter - occurs at idle or with slight acceleration from a stop	Powertrain mount(s)
Groan	Transmission
Howl/groan type noise – pitch increases or changes depending on vehicle speed	Powertrain mount(s)
Dull sound	Transmission
Clunk – occurs when shifting out of PARK or between REVERSE and DRIVE.	Engine mounts Idle speed too high
Howl	Air induction Engine mounts
Accessory drive bearing whine – occurs at idle or high idle at low temperatures of approximately 4 °C or colder, or at the start of the day	Accessory drive tensioner pulley or tensioner pulley bearing binding/slipping between the bearing balls and bearing race
Accessory drive belt noise, squeal or chirp	Faulty, worn, or incorrect accessory drive belt Misaligned pulley(s) Pulley runout Damaged or worn accessory drive component or tensioner pulley Fluid contamination of accessory drive belt or pulleys Accessory drive belt tensioner damaged or worn Damaged pulley grooves Coolant pump pulley damaged or worn
Pop noise – occurs approximately 30 seconds after a cold start.	Turbocharger wastegate
Knock/groan/scrape	Coolant pump has excessive end play or imbalance
Humming	Air induction Engine mounts
Whining	FEAD
Whine/hum – occurs when unlocking the vehicle or opening a door with the engine off (GTDI only)	Fuel pump module
Howl or groaning noise	Air intake system
Whistling noise – usually accompanied by poor idle quality	Air intake system Turbocharger intake pipe leak Loose connections or damaged air intake hoses and tubes Air leaks at the turbine housing, blown connections, or damaged exhaust Carbon buildup on the turbine housing Turbocharger imbalance due to foreign object damage Inoperative turbocharger wastegate valve
Howl or airflow-type noise	Turbocharger Air induction
Chirp or whistling sound	Turbocharger wastegate Air induction
Hissing noise	Air induction
Hissing noise – occurs at idle or high idle speed, and is noticeable with the hood open.	Vacuum leak Vehicles with plastic intake manifold
Scraping noise – occurs when cranking the engine.	Incorrect starter installation Starter motor Starter drive engaging incorrectly Transmission
Engine noise, front of engine – knock at the lower front of the engine	Damaged or detached crankshaft pulley/damper
Press	Transmission Piston
Engine noise, front of engine – ticking, tapping, or rattling at the front of the engine	Timing drive components
Engine noise, upper end – ticking noise near the fuel rail and intake manifold	Fuel rail clamp Fuel Injector HPFP (direct injection engines only)
Engine noise, upper end – ticking, tapping, or rattling occurring at idle or high idle during the first cold start of the day, which may disappear as the engine warms up	Valvetrain noise (collapsed lifter/lash adjuster) Camshaft drive
Engine noise, upper end – occurs mainly when the engine is warm during light/medium acceleration.	Worn or damaged spark plugs
Engine noise, upper end – rattling sound from the valvetrain. Worse when the engine is cold	Low oil level Thin or diluted oil Low oil pressure Worn valvetrain components Worn valve guides Excessive valve seat runout on the valve face
Engine noise, upper end – knock	Gasoline octane rating too low KS operation Incorrect ignition timing High Operating Temperature Spark Plug Catalytic Converter Cylinder head cover Valvetrain
Engine Noise, Lower Part - Ticking or Tapping Noise at the Oil Filter Adapter	Oil Pump Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Engine Noise, Lower Part - Light Knocking Noise, Also Described as Piston Slap. The Noise is Most Noticeable When the Engine is Cold During Light to Medium Acceleration. The Noise Disappears as the Engine Warms Up	Excessive Clearance Between Piston and Cylinder Wall
Engine Noise, Lower Part - Light Double Knock or Sharp Rap Noise. Occurs Mainly at Warm Engine Idle or Low Speeds in Drive. Increases with Engine Load. Associated with Poor Lubrication History	Excessive Clearance Between Piston and Piston Pin
Engine Noise, Lower Part - Light Knocking Noise. The Noise Is Most Noticeable with the Engine Warm. The Noise Tends to Decrease When the Vehicle Is Coasting or in Neutral	Excessive Clearance Between Connecting Rod Bearings and Crankshaft
Engine Noise, Lower Part - Deep Knocking Noise. The Noise Is Most Noticeable with the Engine Warm, at Low RPM and Light Load, and Then When Coasting	Worn or Damaged Crankshaft Main Bearings
Engine Noise, Rear of Engine - Knocking Noise at the Rear of the Engine	Damaged Flywheel/Flex Plate
Slap	Transmission Piston
Knock	Transmission
Engine Vibration - Vibration Felt Constantly	Excessive Engine Pulley Runout Damaged or Worn Accessory Component
Engine Vibration - Low-Frequency Vibration (5-20 Hz) or Light Shake at Idle, Felt Through the Seat / Floor	Cylinder Misfire Engine or Torque Converter Out of Balance
Engine Vibration - Felt as Engine Speed Increases and Decreases	Powertrain mount(s) Engine or Transmission Grounded to Chassis
Engine Vibration - Increases as Engine Speed Increases	Engine Out of Balance
Engine Vibration - Mainly at Coast/Neutral Idle. Condition Improves When the Vehicle Accelerates	Combustion Instability
Engine Vibration or Shudder - Occurs During Light to Medium Acceleration Above 56 km/h	Worn or damaged spark plugs Clogged Fuel Injector Contaminated Fuel
Bongo	Balance Shaft
Chatter	Valvetrain
Chirp	FEAD Piston Rings Valvetrain
Click	Fuel CKP Valvetrain
Rumble	Camshaft drive Piston
Crickets	Camshaft drive
Diesel	Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings Piston
Quack	Camshaft drive FEAD
Scratch	Camshaft drive Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Scrape	Camshaft drive Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Squeak	Camshaft drive Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Squeal	Camshaft drive Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Knock	Transmission Lower end, excessive clearance between connecting rod bearings and crankshaft Lower end, worn or damaged crankshaft main bearings
Tin	Transmission Cylinder head cover Manifold