Ford 2003 Mustang Workshop Manual page 55

Drive the vehicle over a bump or rough surface one wheel at a time to determine if the noise is
coming from the front or the back and the left or the right side of the vehicle.
Proceed as necessary.
Neutral Engine Run-Up (NERU) Test
To carry out this test, proceed as follows:
Install a tachometer.
Increase the engine rpm up from an idle to approximately 4000 rpm while in PARK on front
wheel drive vehicles with automatic transmissions, or NEUTRAL for all other vehicles. Note the
engine rpm and, if possible, determine the vibration frequency.
Attempt to identify what part of the vehicle the concern is coming from.
Attempt to identify the source of the concern.
Proceed as necessary.
Drive Engine Run-Up (DERU) Load Test
To carry out this test, proceed as follows:
WARNING: Block the front and rear wheels, and apply the parking brake and the
service brake, or injury to personnel can result.
CAUTION: Do not carry out the Engine Load Test for more than five seconds or
damage to the transmission or transaxle can result.
Block the front and rear wheels.
Apply the parking brake and the service brake.
Install a tachometer.
Shift the transmission into DRIVE, and increase and decrease the engine rpm between an idle
to approximately 2000 rpm. Note the engine rpm and, if possible, determine the vibration
frequency.
Repeat the test in REVERSE.
If the vibration/noise is duplicated when carrying out this test, inspect the engine and
transmission or transaxle mounts.
If the concern is definitely engine speed-related, carry out the Engine Accessory Test to narrow
down the source.
Proceed as necessary.
Engine Accessory Test
To carry out this test, proceed as follows:
WARNING: Block the front and rear wheels, and apply the parking brake and the
service brake, or injury to personnel can result.
CAUTION: Limit engine running time to one minute or less with belts removed or
serious engine damage will result.