Intake Rocker Arm Diagnosis and Testing

Tools Required

• EN 46339  Intake Rocker Arm Testing Adapter. See Special Tools .
• EN 46340  Intake Rocker Arm Testing Air Stopper. See Special Tools .
• EN 46348  Intake Rocker Arm Testing Air Pressure Regulator and Hose. See Special Tools .
• EN 46352  Intake Rocker Arm Testing Air Adapter. See Special Tools .

1. Start the engine and let it run for 5 minutes.
2. Turn the ignition to the OFF position.
3. Remove the intake air duct.
4. Remove the brake booster vacuum hose from the intake manifold.
5. Remove the ignition coils. Refer to Valve Rocker Arm Cover Removal - Left Side  and Valve Rocker Arm Cover Removal - Right Side .
6. Remove the intake manifold. Refer to Intake Manifold Removal .
7. Remove the valve rocker arm covers. Refer to Valve Rocker Arm Cover Removal - Left Side  and Valve Rocker Arm Cover Removal - Right Side .
Fig 1: Aligning The Upper Cover Mark With Mark On Camshaft (Number 1 Cylinder)
Courtesy of GENERAL MOTORS CORP.
8. Rotate the engine and set number 1 piston at top dead center (TDC). In this position, the mark on the camshaft sprocket (1) will align with the pointer on the cover (2).
Fig 2: Aligning Mark On The Crankshaft Balancer With Pointer On Front Cover
Courtesy of GENERAL MOTORS CORP.
9. With the engine rotated and positioned with number 1 piston at TDC, the alignment mark on the crankshaft balancer (1) will also be aligned with the pointer (2) on the front cover.
Fig 3: View Of Mid Rocker Arm
Courtesy of GENERAL MOTORS CORP.
10. Push on the intake mid rocker arm (2) for the number 1 cylinder. The mid rocker arm should move independently of the primary (1) and secondary (3) rocker arms.
    • If the intake mid rocker arm does not move, remove the mid, primary, and secondary intake rocker arms as an assembly. Check that the pistons in the mid and primary rocker arms move smoothly. Refer to Valve Rocker Arm and Shaft Removal  and Valve Rocker Arm and Shaft Cleaning and Inspection  .
    • If any of the rocker arm requires replacement, replace the primary, mid, and secondary rocker arms as an assembly and test again.
11. Repeat Steps 9 and 10 on each of the remaining intake mid rocker arms with the piston of the cylinder to be tested at TDC.
IMPORTANT: In order to properly test the rocker arms, the shop air supply must be higher than 690 kPa (100 psi).
12. Inspect the valves for proper valve adjustment. Refer to Valve Lash Adjustment .
13. Cover the timing belt with a shop towel to protect the belt.
Fig 4: Identifying Intake Rocker Arm Shaft Mounting Bolts
Courtesy of GENERAL MOTORS CORP.
14. Remove the 2 end intake rocker arm shaft mounting bolts and install the EN 46339  (3), EN 46340  (4), EN 46348  (1) and the EN 46352  (2). See Special Tools .
15. Connect the shop air supply.
16. Loosen the valve on the regulator and adjust the air pressure to 440-540 kPa (64-78 psi).
Fig 5: View Of Mid Rocker Arm
Courtesy of GENERAL MOTORS CORP.
IMPORTANT: If the synchronizing pistons do not move after applying shop air pressure, move the primary and secondary rocker arms up and down manually.
17. Ensure the primary rocker arm (2) and intake secondary rocker arm (1) are mechanically connected by the piston and that the mid rocker arm does not move independently when pushed manually. If any intake mid rocker arms move independently of the primary and secondary rocker arms, replace the rocker arms as an assembly.
18. Inspect the valve lash adjusters. Replace lash adjusters that do not move smoothly. Refer to Valve Lash Adjuster Cleaning and Inspection .
19. Upon completion, inspect and ensure the Service Engine Soon lamp is not illuminated.