Econoline E350 1 Ton V8-5.4L Prop SOHC VIN Z (1998)
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When was it first noticed?
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Did it appear suddenly or gradually?
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Did any abnormal occurrence coincide with or proceed it's appearance?
Use the information gained from the customer to accurately begin the diagnostic process.
2. Pre-Drive Check
It is important to do a pre-drive check before road testing the vehicle. A pre-drive check verifies that the vehicle is relatively safe to drive and
eliminates any obvious faults on the vehicle.
The pre-drive check consists of a brief visual inspection. During this brief inspection, take note of anything that will compromise safety during the road
test and make those repairs/adjustments before taking the vehicle on the road.
3. Preparing For the Road Test
Observe the following when preparing for the road test:
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Review the information recorded on the NVH Diagnostic Guide. It is important to know the specific concern the customer has with the vehicle.
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Do not be misled by the reported location of the noise/vibration. The cause can actually be some distance away.
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Remember that the vibrating source component (originator) may only generate a small vibration. This small vibration can in turn cause a larger
vibration/noise to emanate from another receiving component (reactor), due to contact with other components (transfer path).
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Conduct the road test on a quiet street where it is safe to duplicate the vibration/noise. The ideal testing route is an open, low-traffic area where it is
possible to operate the vehicle at the speed in which the condition occurs.
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If possible, lower the radio antenna in order to minimize turbulence. Identify anything that could potentially make noise or be a source of wind noise.
Inspect the vehicle for add-on items that create vibration/noise. Turn off the radio and the heating and cooling system blower.
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The engine speed is an important factor in arriving at a final conclusion. Therefore, connect an accurate tachometer to the engine, even if the vehicle
has a tachometer. Use a tachometer that has clearly defined increments of less than 50 rpm. This ensures an exact engine speed reading.
4. Verify the Customer Concern
Verify the customer concern by carrying out a road test, an engine run-up test, or both.
The decision to carry out a road test, an engine run-up test, or both depends on the type of NVH concern. A road test may be necessary if the symptom
relates to the suspension system or is sensitive to torque. A drive engine run-up (DERU) or a neutral engine run-up (NERU) test identifies noises and
vibrations relating to engine and drivetrain rpm. Remember, a condition will not always be identifiable by carrying out these tests, however, they will
eliminate many possibilities if carried out correctly.
5. Road Test
Note:
It may be necessary to have the customer ride along or drive the vehicle to point out the concern. During the road test. take into consideration the
customer's driving habits and the driving conditions. The customer's concern just may be an acceptable operating condition for that vehicle.
The following is a brief overview of each test in the order in which it appears. A review of this information helps to quickly identify the most appropriate
process necessary to make a successful diagnosis. After reviewing this information, select and carry out the appropriate test(s), proceeding to the next
step of this process.
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The Slow Acceleration Test is normally the first test to carry out when identifying an NVH concern, especially when a road test with the customer is
not possible.
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The Heavy Acceleration Test helps to determine if the concern is torque-related.
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The Neutral Coast Down Speed Test helps to determine if the concern is vehicle speed-related.
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The Downshift Speed Test helps to determine if the concern is engine speed-related.
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The Steering Input Test helps to determine how the wheel bearings and other suspension components contribute to a vehicle speed-related concern.
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The Brake Test helps to identify vibrations or noise that are brake related.
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The Road Test Over Bumps helps isolate a noise that occurs when driving over a rough or bumpy surface.
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The Engine Run-Up Tests consist of the Neutral Run-up Test and the Engine Load Test. These tests help to determine if the concern is engine
