Ford Falcon. Manual - part 9

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Noise, Vibration and Harshness  

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DIAGNOSIS AND TESTING (Continued)

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Noise, Vibration and Harshness  

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DIAGNOSIS AND TESTING (Continued)

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Noise, Vibration and Harshness  

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DIAGNOSIS AND TESTING (Continued)

The engine speed is an important factor in arriving

1: Customer Interview

at a final conclusion. Therefore, connect an

The diagnostic process starts with the customer

accurate tachometer to the engine, even if the

interview. The service advisor must obtain as much

vehicle has a tachometer. Use a tachometer that

information as possible about the concern and take a

has clearly defined increments of less than 50

test drive with the customer. There are many ways a

rpm. This ensures an exact engine speed reading.

customer will describe NVH concerns and this will

help minimize confusion arising from descriptive

4: Verify the Customer Concern

language differences. It is important that the concern

Verify the customer concern by carrying out a road

is correctly interpreted and the customer descriptions

test, an engine run-up test, or both.

are recorded. During the interview, ask the following

The decision to carry out a road test, an engine

questions:

run-up test, or both depends on the type of NVH

When was the concern first noticed?

concern. A road test may be necessary if the

Did the concern appear suddenly or gradually?

symptom relates to the suspension system or is

Did any abnormal occurrence coincide with or

sensitive to torque. A drive engine run-up (DERU) or a

proceed its appearance?

neutral engine run-up (NERU) test identifies noises

and vibrations relating to engine and drivetrain rpm.

Use the information gained from the customer to

Remember, a condition will not always be identifiable

accurately begin the diagnostic process.

by carrying out these tests, however, they will

2: Pre-Drive Check

eliminate many possibilities if carried out correctly.

It is important to do a pre-drive check before road

5: Road Test

testing the vehicle. A pre-drive check verifies that the

NOTE: It may be necessary to have the customer ride

vehicle is relatively safe to drive and eliminates any

along or drive the vehicle to point out the concern.

obvious faults on the vehicle.

During the road test, take into consideration the

The pre-drive check consists of a brief visual

customer’s driving habits and the driving conditions.

inspection. During this brief inspection, take note of

The customer’s concern just may be an acceptable

anything that will compromise safety during the road

operating condition for that vehicle.

test and make those repairs or adjustments before

taking the vehicle on the road.

The following is a brief overview of each test in the

order in which it appears. A review of this information

3: Preparing for the Road Test

helps to quickly identify the most appropriate process

necessary to make a successful diagnosis. After

Observe the following when preparing for the road

reviewing this information, select and carry out the

test:

appropriate test(s), proceeding to the next step of this

Review the information recorded on the NVH

process.

Diagnostic Guide. It is important to know the

The Slow Acceleration Test is normally the first

specific concern the customer has with the

test to carry out when identifying an NVH concern,

vehicle.

especially when a road test with the customer is

Do not be misled by the reported location of the

not possible.

noise or vibration. The cause can actually be

The Heavy Acceleration Test helps to determine if

some distance away, transferred from another

the concern is torque-related.

part of the vehicle.

The Neutral Coast Down Speed Test helps to

Remember that the vibrating source component

determine if the concern is vehicle speed-related.

(originator) may only generate a small vibration.

This small vibration can in turn cause a larger

The Downshift Speed Test helps to determine if

vibration or noise to emanate from another

the concern is engine speed-related.

receiving component (reactor), due to contact with

The Steering Input Test helps to determine how

other components (transfer path).

the wheel bearings and other suspension

Conduct the road test on a quiet street where it is

components contribute to a vehicle speed-related

safe to duplicate the vibration or noise. The ideal

concern.

testing route is an open, low-traffic area where it

The Brake Test helps to identify vibrations or

is possible to operate the vehicle at the speed in

noise that are brake-related.

which the condition occurs.

The Road Test Over Bumps helps isolate a noise

If possible, lower the radio antenna in order to

that occurs when driving over a rough or bumpy

minimize turbulence. Identify anything that could

surface.

potentially make noise or be a source of wind

The Engine Run-Up Tests consist of the Neutral

noise. Inspect the vehicle for add-on items that

Run-up Test and the Engine Load Test. These

create vibration/noise. Turn off the radio and the

heating and cooling system blower.

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Noise, Vibration and Harshness  

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DIAGNOSIS AND TESTING (Continued)

tests help to determine if the concern is engine

Downshift Speed Test

speed-related.

To carry out this test, proceed as follows:

The Neutral Run-up Test is used as a follow-up

Shift into a lower gear than the gear used when

test to the Downshift Speed Test when the

carrying out the Slow Acceleration Test.

concern occurs at idle.

Drive at the engine rpm where the concern

The Engine Load Test helps to identify

occurs.

vibration/noise sensitive to engine load or torque.

The concern is engine speed related if duplicated

It also helps to reproduce engine speed-related

while carrying out this test. This eliminates the

concerns that cannot be duplicated when carrying

tyres, wheels, brakes and the suspension

out the Neutral Run-up Test or the Neutral Coast

components as sources.

Down Test.

If necessary, repeat this test using other gears

The Engine Accessory Test helps to locate faulty

and NEUTRAL to verify the results.

belts and accessories that cause engine

speed-related concerns.

Proceed as necessary.

The Vehicle Cold Soak Procedure helps to

Steering Input Test

identify concerns occurring during initial start-up

and when an extended time lapse occurs between To carry out this test, proceed as follows:

vehicle usage.

Drive at the speed where the concern occurs,

while making sweeping turns in both directions.

Slow Acceleration Test

If the concern goes away or gets worse, the

To carry out this test, proceed as follows:

wheel bearings, hubs, U-joints (contained in the

Slowly accelerate to the speed where the reported

axles of 4WD applications), and tyre tread wear

concern occurs. Note the vehicle speed, the

are all possible sources.

engine rpm and, if possible, determine the

Proceed as necessary.

vibration frequency.

Brake Test

Attempt to identify from what part of the vehicle

the concern is coming.

To carry out this test, proceed as follows:

Attempt to identify the source of the concern.

Warm the brakes by slowing the vehicle a few

Proceed as necessary.

times from 80–32 km/h (50–20 mph) using light

braking applications. At highway speeds of 89–97

Heavy Acceleration Test

km/h (50–60 mph), apply the brake using a light

pedal force.

To carry out this test, proceed as follows:

Accelerate to 89–97 km/h (55–60 mph).

Accelerate hard from 0-64 km/h (0-40 mph).

Lightly apply the brakes and slow the vehicle to

Decelerate in a lower gear.

30 km/h (20 mph).

The concern is torque-related if duplicated while

A brake vibration noise can be felt in the steering

carrying out this test.

wheel, seat or brake pedal. A brake noise can be

Proceed as necessary.

heard upon brake application and diminish when

Neutral Coast Down Speed Test

the brake is release.

To carry out this test, proceed as follows:

Road Test Over Bumps

Drive at a higher rate of speed than where the

To carry out this test, proceed as follows:

concern occurred when carrying out the Slow

Drive the vehicle over a bump or rough surface

Acceleration Test.

one wheel at a time to determine if the noise is

Place the transmission in NEUTRAL and coast

coming from the front or the back and the left or

down past the speed where the concern occurs.

the right side of the vehicle.

The concern is vehicle speed-related if duplicated

Proceed as necessary.

while carrying out this test. This eliminates the

engine and the torque converter as sources.

Neutral Engine Run-up (NERU) Test

If the concern was not duplicated while carrying

To carry out this test, proceed as follows:

out this test, carry out the Downshift Speed Test

Install a tachometer.

to verify if the concern is engine speed-related.

Increase the engine rpm up from an idle to

Proceed as necessary.

approximately 3,500 rpm while in PARK on front

wheel drive vehicles with automatic transmissions,

or NEUTRAL for all other vehicles. Note the

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