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100-04-6
Noise, Vibration and Harshness
100-04-6
DIAGNOSIS AND TESTING
2. AccelerationIDeceleration: With slow
acceleration and deceleration, a shake is
sometimes noticed in the steering wheellcolumn,
seats, front floor panel, front door trim panel or
front end sheet metal. It is a low frequency
vibration (around 9-1 5 cycles per second). It
may or may not be increased by applying the
brakes lightly. REFER to Idle
BoomIShakeNibration in the Driveline Noise
and Vibration Symptom Chart.
High Speed: A vibration is felt in the front floor
panel or seats with no visible shake, but with
an accompanying sound or rumble, buzz, hum,
drone or booming noise. Coast with the clutch
pedal depressed (manual transmission) or shift
control selector lever in "N" (NEUTRAL)
(automatic transmission) and engine idling. If
vibration is still evident, it may be related to
wheels, tires, front brake discs, wheel hubs or
front wheel bearings. REFER to Shake and
Vibration While Driving in the Driveline Noise
and Vibration Symptom Chart.
4. Engine rpm Sensitive: A vibration is felt
whenever the engine reaches a particular rpm.
It will disappear in neutral coasts. The vibration
can be duplicated by operating the engine at
the problem rpm while the vehicle is stationary.
It can be caused by any component, from the
accessory drive belt to the clutch or torque
converter which turns at engine speed when the
vehicle is stopped. REFER to Shake and
Vibration While Driving in the Driveline Noise
and Vibration Symptom Chart.
5. Noise and Vibration While Turning: Clicking,
popping or grinding noises may be due to the
following:
worn, damaged or incorrectly installed front
wheel bearing.
damaged powertrainldrivetrain mounts.
Road Conditions
An experienced technician will always establish a
route that will be used for all NVH diagnosis road
tests. The road selected should be reasonably
smooth, level and free of undulations (unless a
particular condition needs to be identified). A
smooth asphalt road that allows driving over a
range of speeds is best. Gravel or bumpy roads
are unsuitable because of the additional road noise
produced. Once the route is established and
consistently used, the road noise variable is
eliminated from the test results.
N0TE:Some concerns may be apparent only on
smooth asphalt roads.
If a customer complains of a noise or vibration on
a particular road and only on a particular road, the
source of the concern may be the road surface. If
possible, try to test the vehicle on the same type
of road.
Vehicle Preparation
Carry out a thorough visual inspection of the
vehicle before carrying out the road test. Note
anything which is unusual. Do not repair or adjust
any condition until the road test is carried out,
unless the vehicle is inoperative or the condition
could pose a hazard to the technician. After
verifying that the condition has been corrected,
make sure all components removed have been
installed.
Power Steering Conditions
c
!
Check for the noise in the following conditions to
verify the customer concern.
Check for the noise in several temperature
conditions.
Is the noise from when the vehicle was new?
Can the noise be repeated constantly or is it
random?
Check the condition of the vehicle age, mileage
and service record.
Interview the customer to find the operating
condition in which the noise will occur. Test the
vehicle based on the detail(s) from the customer
interview.
Follow the power steering operation noise
condition tables below, to find which condition
the noise will occur.
Power Steering Operation Noise Check
Step 1 : Check for NVH concerns from non-steering
components, which may sound like noises coming
from the steering system.
I : .
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2006.0 Fiesta
121zoo6
G37349en
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