GM Service Manual Online
For 1990-2009 cars only
  1. Remove the engine front cover. Refer to Engine Front Cover Removal .
  2. Remove the spark plugs. Refer to Spark Plug Replacement in Engine Controls.

  3. Object Number: 648539  Size: MH

    Important: 

       • The timing marks must be correctly aligned before disassembly in order to correctly install the timing chains.
       • Avoid turning the camshafts and the crankshaft once the timing chain is removed. Valve and piston damage may occur.

  4. Rotate the crankshaft so that the following conditions are met:
  5. • The keyway on the crankshaft (3) is properly positioned.
    • The arrow (2) on the idler sprocket is pointing to the crankshaft.
    • The marks on the sprockets (1) match up with the marks on the cylinder head.
  6. Remove the 3 bolts and the upper chain guide.

  7. Object Number: 648565  Size: SH
  8. Remove the 1 nut and 2 bolts from the timing chain tensioner (1).
  9. Remove the timing chain tensioner (1). It may be necessary to slacken the timing chain by turning the intake camshaft (2) counterclockwise a little while pushing back on the tensioner pad.

  10. Object Number: 648553  Size: SH
  11. Hold the camshafts (2) with a wrench and remove the camshaft sprocket bolts.
  12. Remove the camshaft sprockets (1, 3) and timing chain.

  13. Object Number: 648578  Size: SH
  14. Remove the 2 bolts (1) and the side chain guide (2).