Diagnosis and verification of noise, vibration and harshness (NVH)

Inspection and verification

• 1. Check the validity of the customer's complaint.
• 2. Visually inspect for obvious signs of mechanical or electrical damage.
• 3. If an obvious cause of the problem you identified or described by the client is found, eliminate it before proceeding to further actions (if possible).
• 4. If the problem is not visually obvious, check the symptom and refer to the Symptom Chart.

How to use this section of diagnostic procedures

• Noise, vibration and harshness issues (NVH) have become very important, because cars have become more susceptible to such influences. This section will help identify such situations.
• This section provides information on diagnostic procedures based on a particular symptom. If, for example, the problem occurs at high vehicle speeds, the most appropriate place to start diagnosing is the «Shaking and vibration at high speed».
• The road test procedure will tell you how to categorize conditions and how to distinguish vibration from shaking.
• To ensure that the cause is either identified or corrected, a series of quick checks are performed during the road test.
• Decide on the name of the condition, go to the appropriate section and find the correct diagnostic technique. After the state is identified, the work is partially completed.
• Follow the prescribed diagnostic procedure.
• The quick checks are described within a single step, while the more complex checks and adjustments are described in the chapter «General procedures».
• Always follow the sequence of each step exactly and make notes so that you can track down any important points later.

Customer survey

Road test and customer survey (if possible) provide information that will help identify the problem and indicate where to start diagnosing.

State Identification

Noise, vibration and harshness (NVH) usually appear in four areas:

• tires
• engine accessories
• suspension
• transmission

Therefore, it is necessary, as far as possible, to reduce the problem of NVH to these specific areas. The easiest and fastest way to do this is to complete the prescribed road test. Use a certified tester to diagnose NVH problems to facilitate diagnostics and verification procedures.

Noise Diagnosis Procedure

Noise not related to vehicle axles

The five most common sources of non-axle noise are the exhaust system, tires, roof rack, trim panels and transmission.

Therefore, before disassembling and diagnosing the transmission, make sure that none of the following conditions is the cause of the noise.

• Under certain conditions, the emission of exhaust gases can cause a sound very similar to «mechanical» noise. In other cases, it can be mistaken for wheel bearing rumble.
• Tires, especially winter tires, can cause a high-pitched whine or tread roar similar to «mechanical» noise. This characteristic, to some extent, have radial tires. In addition, non-standard tires with an atypical tread pattern can also cause howling or roaring.
• Trim panels can also cause whistling or howling noises.
• A dull metallic sound can be heard when the ranges are turned on «R» And «D» in an automatic transmission or when the throttle is applied or released. Noise can be caused by side clearances present in the transmission.
• The rattling in the bearings is like the sound of glass balls colliding. This condition is usually caused by wheel bearing failure.

Noises

• «Mechanical» noise is usually a roar or whine caused by damage in the mechanism or improper bearing preload. It can manifest itself at various speeds and driving conditions. Such noise may be permanently present.
• «Cackle» is a certain rattling noise that sounds like a stick caught in the spokes of a rapidly spinning bicycle wheel. This happens when decelerating from a speed of 64 km/h (40 mph), and usually such noise can be heard all the way from deceleration to a complete stop. The frequency changes with vehicle speed.
• The knock is very similar to «cackle», although it could be quieter. It occurs when accelerating or decelerating. Disassembly will show what needs to be fixed.

Clicking, popping or grinding noises can be caused by:

• wear, damage or improper installation of wheel bearings, suspension components or brake systems.

Before dismantling the gearbox in the block with the driving axle, in order to diagnose and eliminate «mechanical» noise, check tires, exhaust system and trim.

Noises described in the chapter «road test», usually have specific causes that can be diagnosed by observing the assembly as it is disassembled. The primary clues are the nature of the noise heard during the road test and the driving conditions.

Vibration

Vibration at high speeds can be caused by:

• imbalance of the front or rear wheels;
• deviation of the shape of the tires from the shape of the circle (ovality).

Vibration, jitter when accelerating can be caused by the following:

• damage to the supports of the power unit / transmission;
• excess of working angles in the hinges of equal angular velocities (SHRUS): this is caused by incorrect ride height; Check the ride height, the correct characteristics of the springs and the components in a non-working condition.

Road test

Any mechanically driven assembly will produce some kind of noise during operation. Some noises are acceptable and can be heard at certain speeds or under various driving conditions such as driving on newly paved asphalt roads. Slight noise is not an indicator of a malfunction and can be considered normal.

Road test and customer survey (if possible) provide information that helps identify the problem and suggests the best place to start diagnosing.

• 1. Take notes during the diagnostic process. Write down even insignificant information, because things can turn so that this information becomes the most important information.
• 2. Do not touch anything until a road test has been carried out and a thorough visual inspection of the vehicle has been completed. Leave the tire pressure and vehicle load as they were when the fault condition was first observed. Adjusting tire pressure, vehicle load, or making other adjustments may help reduce «intensity» manifestation of a problem state to a level at which it is no longer possible to clearly identify the problem. In addition, it may introduce something new into the system that prevents correct diagnosis.
• 3. Perform a visual inspection (part of the pre-diagnosis), writing down everything that seems wrong to you. Make a note of the tire pressure, but do not adjust the pressure yet. Make a note of any leaks, loose nuts and bolts, places where items can rub against each other. Check the cargo compartment for unusual loads.
• 4. Carry out a road test, during which, by repeatedly reproducing the problem condition, determine the nature of the malfunction.
• 5. After reproducing the status, perform quick checks. This will reveal the correct diagnostic procedure. To make sure that quick checks give the correct result, run them several times. Remember that quick checks performed during a road test will not tell you what the problem is (Where), but will show where it is not.

Quick checks during the road test

1. At a speed of 24-80 km/h (15-50 mph): When accelerating lightly, a groan is heard and vibration may be felt in the front area of the floor. Usually the situation worsens when accelerating at this speed at a certain engine speed and a certain throttle position. A groaning sound may be present, depending on the element causing the sound. Refer to the Troubleshooting Table, chap. «Moaning sound of variable pitch».


2. Acceleration/Deceleration: When accelerating or decelerating slowly, the steering wheel/column, seats, front floor, front door trim panels, or front body parts of the vehicle will sometimes experience shaking. This is a low frequency vibration (approximately 9 - 15 cycles per second). With light application of the brakes, it may or may not increase. Refer to the Troubleshooting Table, chap. «Humming / shaking / vibration at idle».

3. High speed: Vibration is felt without visible shaking in the front of the floor or seats, but accompanied by a rumble, hum, hum.. Coast with the clutch pedal depressed (Manual Transmission) or gear lever in neutral position (Automatic transmission) or when the engine is idling. If the vibration is still present, it is related to the wheels, tires, front brake discs, wheel hubs, or front wheel bearings. Refer to the Troubleshooting Table, chap. «Shaking and vibration at high speed».

4. Engine Speed Sensitivity: Vibration is felt whenever the engine reaches a certain engine speed. It will disappear when coasting in neutral gear. Vibration can also be reproduced when the vehicle is stationary by bringing the engine speed to the problematic speed. It can be caused by anything from an accessory drive belt to a clutch or torque converter that rotates at engine speed when the vehicle is stationary. Refer to the Troubleshooting Table, chap. «Shaking and vibration while driving».

5. Noise and vibration when cornering: Clicking, popping or grinding noises can be caused by:

• wear, damage or improper installation of front wheel bearings;
• damage to the powertrain/transmission mounts.

Road conditions

An experienced technician will always map out the route that he will use for all road tests when diagnosing NVH. The selected road must be reasonably smooth, level and free of bumps (potholes and potholes) (if not required to identify a specific problem state). A flat asphalt road is preferred, which allows testing over the entire speed range. Gravel and bumpy, bumpy roads are not suitable. moving along them is accompanied by additional noise. Once a route has been developed and consistently used, the road noise component can be isolated from the test results.

NOTE: Some problem conditions may only occur on smooth asphalt roads.

If a customer is complaining about noise or vibration on a particular road, and only on that particular road, the road surface may be a source of concern. If possible, try to test the vehicle on the same type of road.

Car preparation

Perform a thorough visual inspection before performing a road test. MARK anything unusual. If the car is operational, and the malfunction cannot harm the technician, do not touch anything (do not serve, do not regulate) before the road test.

After confirming that the problem has been corrected, make sure that all items removed during the repair are installed in place.

State	Possible Causes	Action
• Shaking and vibration when driving	• Vibration of the front of the car • Engine/transmission.	• Go to PINPOINT TEST A
• Moaning sound of variable pitch	• Air filter • Power steering (PAS). • Power unit • Powertrain/transmission mountings • Exhaust system	• Go to PINPOINT TEST B
• Humming/shaking/vibration or twitching at idle	• Ropes/cables/hoses • Powertrain/transmission mountings • Exhaust system • Drive belts/pulleys	• Go to PINPOINT TEST C
• Front End Vibration Analysis	• Suspension • Wheel bearings	• Go to PINPOINT TEST D
• Noise not related to the bridge	• Finishing panels. • Air conditioning system • Accessories	• Go to PINPOINT TEST E

Pinpoint - tests

NOTE: Pinpoint tests are intended to help the technician go through a step-by-step diagnostic procedure and ultimately determine the cause of a particular problem condition. It is not always necessary to follow the table to the end. Perform only those Pinpoint test items that are necessary to fix the problem. Then, to make sure that everything is in order, check the operation of the system.

After confirming that the problem has been corrected, make sure that all items removed during the repair are installed in place.

PINPOINT TEST A: SHAKING AND VIBRATION WHILE MOVING

STATES	DETAILS/RESULTS/ACTIONS
A1: COAST IN NEUTRAL
	1 Carry out a test that requires the vehicle to coast into neutral.
	• Does the vibration disappear when the vehicle coasts in neutral?
	→ Yes
	Go to A2
	→ No
	Go to Pinpoint Test D.
A2: CHECKING THE POWER UNIT/GEARBOX BASES IN THE DRIVE AXLE UNIT
	1 Visually CHECK the condition of the powertrain/gearbox hydraulic mounts in the transaxle assembly for leaks.
	• Are the powertrain/gearbox mountings in the drive axle assembly OK?
	→ Yes
	Go to A3
	→ No
	Go to Pinpoint Test D.
A3: VERIFICATION OF POWER UNIT / GEARBOX ALIGNMENT IN UNIT WITH DRIVE AXLE
	1 Follow the engine/transaxle mount alignment procedure in this section.
	• Has shaking and vibration been eliminated?
	→ Yes
	The car is correct. REPEAT the prescribed road test.
	→ No
	Check the customer's complaint.

PINPOINT TEST B: MOANING SOUND OF VARIABLE Pitch

STATES	DETAILS/RESULTS/ACTIONS
B1: AIR FILTER CHECK
	1 Check the air filter. - Check the air filter, the condition of the air filter supports, the correct installation and tightness of all connections of the intake piping, exhaust piping, resonators and all other elements associated with the air intake system.
	• Are all items in order?
	→ Yes
	Navigate to B2
	→ No
	REPAIR faults/defects. REPEAT the prescribed road test.
B2: EXHAUST SYSTEM CHECK
	1 Check exhaust system mounts.
	• Are the exhaust system mountings in order?
	→ Yes
	Go to B3
	→ No
	INSTALL new supports if necessary. REPEAT the prescribed road test.
B3: POWER STEERING CHECK
	1 Remove the accessory drive belt and listen for a groaning sound.
	• Has the groaning sound been eliminated?
	→ Yes
	PERFORM power steering repairs as needed. Refer to Section 211-02 for more information.
	→ No
	Go to B4
B4: CHECKING ENGINE/GEARBOX MOUNTINGS WITH DRIVE AXLE
	1 Visually CHECK the condition of the powertrain/gearbox hydraulic mounts in the transaxle assembly for leaks.
	• Are the powertrain/gearbox mountings in the drive axle assembly OK?
	→ Yes
	Go to B5
	→ No
	Install new supports if necessary. REPEAT the prescribed road test.
B5: POWER UNIT/GEARBOX ALIGNMENT CHECK
	1 Follow the engine/transaxle mount alignment procedure in this section.
	• Has the groaning sound been eliminated?
	→ Yes
	The car is correct. REPEAT the prescribed road test.
	→ No
	Check the customer's complaint.

PINPOINT TEST C: HORNING/ SHAKING/ VIBRATION/ JERKING WHEN IDLING

STATES	DETAILS/RESULTS/ACTIONS
C1: ROPE/CABLE/HOSE CHECK
	1 Check the engine compartment for any items that may be hanging between the engine and the body or chassis. For example: control cable, air conditioning hoses (A/C) and accelerator cable.
	• Are the items in order?
	→ Yes
	Go to C2
	→ No
	REPAIR the problem/defect. REPEAT the prescribed road test.
C2: ENGINE COOLING RADIATOR CHECK
	1 Check the cooling system radiator supports and bushings for security and condition. Check the position of the radiator in relation to other elements that may touch it (touching is not allowed).
	• Is the position correct and are the earbuds OK?
	→ Yes
	Go to C3
	→ No
	REPAIR or INSTALL new items as needed. REPEAT the prescribed road test.
C3: EXHAUST SYSTEM CHECK
	1 Check exhaust system mounts.
	• Are the exhaust system mountings in order?
	→ Yes
	Go to C4
	→ No
	INSTALL new supports if necessary. REPEAT the prescribed road test.
C4: INSPECTION OF POWER UNIT/GEARBOX SUPPORTS WITH DRIVE AXLE
	1 Visually CHECK the condition of the powertrain/gearbox hydraulic mounts in the transaxle assembly for leaks.
	• Are the powertrain/gearbox mountings in the drive axle assembly OK?
	→ Yes
	Go to C5
	→ No
	Install new supports if necessary. REPEAT the prescribed road test.
C5: POWER UNIT/GEARBOX ALIGNMENT CHECK
	1 Follow the Powertrain/Transaxle Mount Alignment Procedure in this section.
	• Has the humming/ shaking/ vibration/ twitching been eliminated?
	→ Yes
	The car is correct. REPEAT the prescribed road test.
	→ No
	Check the customer's complaint.

PINPOINT TEST D: FRONT VIBRATION

STATES	DETAILS/RESULTS/ACTIONS
D1: TIRE INSPECTION
	1 Inspect wheels and tires. See Section 204-04 for more information.
	• Are the wheels and tires OK?
	→ Yes
	Go to D2
	→ No
	INSTALL new wheels and tires as needed. Refer to Section 204-04 for more information. REPEAT the prescribed road test.
D2: WHEELS AND TIRES RUN AND INSPECTION
	1 Inspect and check wheel and tire runout. Refer to Section 204-04 for more information.
	• Are wheel and tire runouts within specifications?
	→ Yes
	Go to D3
	→ No
	MAKE necessary repairs. Refer to Section 204-04 for more information. REPEAT the prescribed road test.
D3: WHEEL BEARING INSPECTION
	1 Inspect wheel bearings. See Section 204-00 for more information.
	• Are the wheel bearings OK?
	→ Yes
	Check the customer's complaint.
	→ No
	INSTALL new wheel bearings if necessary. REPEAT the prescribed road test.

PINPOINT TEST E: NON-VEHICLE AXLE NOISE

STATES	DETAILS/RESULTS/ACTIONS
E1: VEHICLE FINISH INSPECTION
	1Check the grille and trim panels to see if they are sources of noise.
	• Are there any finishes that cause noise?
	→ Yes
	INSTALL new trims or REPAIR as necessary.
	→ No
	Go to E3
E2: CHECK THE HEATING AND VENTILATION SYSTEM FOR NOISE GENERATION
	1 Drive the START position.
	2 Drive the ON position.
	3 Check HVAC components for noise generation by turning the HVAC system on and off.
	• Does the heating and ventilation system generate noise?
	→ Yes
	PERFORM HVAC System Diagnosis. Refer to Section 412-02A / 412-02B for more information.
	→ No
	Go to E3
E3: AIR CONDITIONING CHECK (A/C) TO GENERATE NOISE
	1 Check the A/C system components for noise generation by turning the A/C system on and off.
	• Is the A/C system generating noise?
	→ Yes
	Diagnose the A/C system. Refer to Section 412-00 for more information.
	→ No
	Go to E4
E4: CHECKING NON-FACTORY INSTALLED ACCESSORIES
	1 Check all accessories for noise generation. Example: touching the body and frame, antennas, sun visors and fog lights.
	• Are the accessories generating noise?
	→ Yes
	Adjust, repair or install new accessories.
	→ No
	Check the customer's complaint.

Powertrain/Transmission Mount Alignment

NOTE: There is no powertrain/transmission mount alignment procedure. To check the alignment of the power unit supports visually, follow these steps:

1. Loosen the rear support pad mounting bolts (in the presence of).

2. Release bolts of fastening of the power unit/gearbox in the block with the driving axle.

3. NOTE: Support the power package/gearbox in the drive axle assembly at the approximate horizontal and vertical position.

NOTE: Make sure that the position of the right leg and left pad matches the studs on the powertrain and transaxle in the drive axle assembly to allow the fasteners to be inserted into the large holes in the pad bracket without undue stress in them.

Check the alignment of the powertrain/gearbox mountings in the drive axle assembly.

4. Tighten bolts of fastening of the power unit/gearbox in the block with the driving axle to an arm of a support.

5. Tighten bolts of fastening of a support of the power unit/gearbox in the block with the driving axle to a body.

6. Tighten the rear support pad mounting bolts (in the presence of).