GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

Are dull thuds or knocks heard with every engine revolution?

--

Go to Step 2

System OK

2

Inspect the oil pump pressure.

Is the oil pump pressure low?

--

Go to Oil Pressure Diagnosis and Testing

Go to Step 3

3

Inspect the crankshaft end play.

Does the crankshaft end play exceed the specified value?

0.1 mm (0.003 in)

Go to Crankshaft Replacement

Go to Step 4

4

Inspect the crankshaft journals.

Are the crankshaft journals out-of-round?

0.004 mm (0.0002 in) max

Go to Crankshaft Replacement

Go to Step 5

5

Inspect the belt tension.

Is a repair necessary?

--

Go to Timing Belt Replacement

Go to Step 6

6

Inspect the crankshaft pulley

Is the crankshaft pulley loose?

--

Go to Crankshaft Replacement

System OK