GMC Chevrolet Camaro 1998 Service Manual page 73

General Information
Inherent Engine Shaking Forces
Engine Order Vibration Table
Engine Order VB 90°
1/2 Order Torque Sensitive Single Cylinder Misfire
1st Order Imbalance Abnormal
1.5 Order Torque Sensitive
-
2nd Order Abnormal
2nd Order Torque Sensitive
Bank-to-Bank
EGR/Fuel Var.
3rd Order Torque Sensitive
-
4th Order Torque Sensitive Normal
183028
Just like firing frequency, some engine disturbances
are the result of normal operation. Some engines
can have additional inherent vibration due to the
cylinder arrangement, the design, and the firing order.
Before attempting to repair a disturbance, compare
the disturbance to another known good vehicle.
Although some vibrations could be normal, they may
not be pleasant to the customer.
The key to resolve an inherent engine disturbance is
to isolate the vibration from the passenger
compartment. Follow the same procedures as outlined
for the engine firing frequency-related vibrations.
Vibration Diagnosis and Correction 0-61
Engine-Driven Accessories
95613
Engine driven accessories that exhibit vibration pose
some special challenges. For example, the drive
belts can no longer be removed one at a time in order
to isolate the condition. If removing the belt eliminates
the vibration, reinstall the belt and operate each
accessory one at a time in order to see which has the
most effect on the vibration. However, one component
may affect another because the drive belt drives all
of the accessories.
Inspect that the accessory load is not exciting the
engine firing frequency.
Diagnosis
1. Compare the vibrations to a known good vehicle
in order to ensure they are abnormal.
2. Remove the drive belts.
3. If the vibration stops, perform the following steps:
3.1. Install the drive belts.
Important: The drive belts drive all of the engine
accessories. Therefore, one component may affect
another.
3.2. Operate each accessory one at a time in
order to see which has the most effect on
the vibration.
4. Inspect for accessory load affecting the engine
firing frequency.
5. Inspect the pulleys for misalignment or bends.
Repair or replace as needed.
6. Inspect the A/C system for overcharging. Evacuate
and Recharge as needed. Refer to Evacuation
and A.C Charging in HVAC Systems with
A/C- Manual.
7. Inspect the engine oil level. Add or drain as
needed.