- Clean the intake manifold in a commercially available cleaning fluid and blow dry using compressed air.
- Ensure the intake manifold gasket grooves and vacuum passages in the rear of the intake manifold are all clean and clear.
- Inspect the throttle body and fuel rail bolt inserts in the intake manifold for looseness and/or damaged threads.
- Inspect the intake manifold for cracks or damage including the areas between the intake runners.
- Inspect the fuel injector bores for excessive scoring or damage.
- Inspect the intake manifold to cylinder head faces for warpage as follows:
| • | Place a straight edge across each of the two surfaces and check for warpage using feeler gauges. |
| • | An intake manifold with warpage in excess of 0.5 mm must be replaced. |
