GMC Chevrolet Camaro 1998 Service Manual page 72

0-60 Vibration Diagnosis and Correction
Engine Vibration Diagnosis with the EVA
INPUT A INPUT B
95611
1. Place the EV A vibration sensor on the seat track
rail with the UP label facing upward.
2. Plug the EVA into a 12-volt power supply.
3. Prepare the EVA for data recording:
3.1. Press RECORD.
3.2. Select a snapshot tag number.
3.3. Press ENTER in order to begin recording.
4. Slowly accelerate until the vibration occurs.
5. Note the vehicle and engine rpm where the
disturbance. occurs.
6. Press ENTER on the EV A in order to record the
vibration data.
7. Perform the road test diagnoses in order to
determine engine-speed or vehicle-speed
sensitivity. Refer to Road Test
Engine Firing Frequency Symptoms
• The vibration may be torque sensitive.
• The vibration is engine-speed related.
• The vibration is heard as a boom or a moan.
• The vibration is felt ass shake, roughness, or buzz
(depending on the number of cylinders).
• The vibration excites the resonance of a system
or a component, causing the system or the
component to have a narrow rpm range.
The key to correcting these types of complaints is to
isolate the vibration from the passenger compartment
or the body.
General Information
Diagnosis and Repair of Engine Firing
Frequency-Related Vibrations
1. Raise and suitably support the vehicle. Refer to
Lifting and Jacking the Vehicle in General
Information.
2. Take the necessary safety precautions. Refer to
Work Stall Test Caution in General Information.
3. Attempt to duplicate the vibration.
4. While the vibration is present, find the area(s) of
the vehicle excited by the vibration.
5. Inspect for witness marks due to a rubbing
component.
6. Isolate the component and re-evaluate the
vibration.
7. Inspect for proper torque on the excited
component(s). Tighten as needed.
8. If the vibration still exists, proceed to the
procedure below.
Engine Firing Frequency-Related Vibration
Causing Components
1 . Inspect for collapsed engine mounts.
Replace as needed. Refer to Engine Mount
Replacement or Engine Mount Replacement
(Right Side)
2. Inspect the exhaust hangers.
• Exhaust systems can expand one to two
inches when hot.
• Remove the hangers one at a time.
• Adjust or replace as needed.
3. Lubricate the manifold flexible coupling.
4. Inspect the A/C and P/S lines.
• Isolate the hoses from the body.
• Install the retainers.
5. Inspect the drive belts for whipping.
6. Inspect the accessory unit fasteners for damage
or looseness.
7. Inspect the body panels for missing or
loose welds.
8. Remove any aftermarket equipment that may
complete a transfer path into the passenger
compartment.
9. Inspect the exhaust system and powertrain
mounts. Re-bed the engine and align the exhaust
system as follows if needed:
• Loosen the mounts and hangers.
• Tighten all fasteners with the powertrain in the
relaxed position.
Some residual vibrations may be normal. Compare the
vibrations with a similar vehicle to get a feel for what is
commercially acceptable, preferably with the customer
present. Also, refer to bulletins for updates on the use of
mass damper weights for specific applications.