Step 2. Carbon Build-Up, Diagnosis

Visually inspect the intake valves and ports for carbon build-up as follows:

- remove # 2 and possibly # 3 fuel injector(s)
- remove # 2 and possibly # 3 injector insert(s)

With piston # 2 at Top Dead Center:

- insert flex light into cylinder intake port through the injector insert opening
- using inspection mirror, determine degree of carbon build-up on intake valve
- compare your observation with the following chart
- re-install insert(s) and fuel injector(s), replace O-ring(s) if necessary