For 1990-2009 cars

1. Inspect the intake manifold for damage.
2. Inspect the intake manifold for cracks near the mounting holes.
3. Inspect the crankcase ventilation passages for any blockage and clean as necessary.
4. Clean the intake manifold mating surfaces.
5. Use a straight edge and a feeler gauge and measure the intake manifold mounting surface for warpage.

Intake Manifold Maximum Warpage
0.10 mm (0.0039 in)

6. If the warpage is greater than the maximum, repair or replace the intake manifold.