GM Service Manual Online
For 1990-2009 cars only

Cause

Correction

Important: The camshaft position actuator may make a slight tapping noise upon cold startup. This is due to the viscosity of the oil that has not yet warmed to proper operating temperatures, and should be considered normal for the first 3.5 minutes of cold engine operation.

Incorrect oil filter without anti-drainback feature

Install the correct oil filter.

Incorrect oil viscosity

  1. Drain the oil.
  2. Install the correct viscosity oil.

Worn crankshaft thrust bearing

  1. Inspect the thrust bearing and crankshaft.
  2. Repair or replace as required.

High valve lifter leak down rate

Replace the lifters as required.

Excessive crank/rod bearing clearances

  1. Inspect the crankshaft and rod bearings.
  2. Repair or replace as required.