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

Measure the oil pump pressure.

Is the oil pump pressure low?

--

Go to Oil Pressure Diagnosis and Testing

Go to Step 3

3

Measure the crankshaft end play.

Does the crankshaft end play exceed the specified values?

0.302 mm (0.0119 in)

Go to Crankshaft Replacement

Go to Step 4

4

Inspect the crankshaft journals.

Are the crankshaft journals out-of-round?

--

Go to Crankshaft Replacement

Go to Step 5

5

Inspect the belt tension.

Is there excessive belt tension?

--

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