To disconnect, remove and uninstall air intake plenum and lower intake manifold, one has to discharge the fuel system pressure, and the negative battery cable should be disconnected. Disconnect the air cleaner assembly and the throttle body, the fuel lines and connectors of each injector. It is recommended that if upper and lower intake manifolds are removed for gasket exchanges or upper engine work only, install the air intake plenum's throttle body and remove both simultaneously. Remove the electrical connectors from the manifold absolute pressure sensor, power switch, and the electronic vacuum sensing valve, if there is a throttle body it is necessary to remove the idle air control valve and throttle position sensor connectors. Remove the accelerator cable and transmission linkage from the throttle body assembly, vacuum the brake booster hose and cut all vacuum lines coming to it and the rest of the vacuum lines as the EVAP canister purge, PCV valve, EGR valve, and fuel pressure regulator. There is no need for an elaborate procedure at this point: you must only unscrew the bolts and nuts of the plenum, and then get the air intake plenum off the lower intake manifold. For the lower intake manifold, it is necessary to disjoint the fuel supply and return hoses, to disconnect the connectors from the fuel injectors and to unbolt and un-nut the manifold. Tap at a corner of the manifold to disturb the gasket seal without compromising on the sealing zones. For installation, the surfaces of the mating members should be clean, the gasket can be chemically removed by using gasket removal solvents, also clean the bolt holes. Place the new gaskets on the
Cylinder Heads and locate the manifold into the position without removing the gaskets; then install bolts, washers, and nuts and over tighten according to the torque. Replace the lower intake manifold gasket on the air intake plenum and locate it into position securing it, and fasten the intake bolts. Last of all, switch on the engine and look at the leakages of the oil and coolant at the intake manifold joints.