Disconnect the battery ground cable and drain the cooling system.
Disconnect the wire harness at the air flow sensor. Remove the air flow sensor as an assembly. Disconnect the air intake hose running from the air flow sensor to the manifold.
Remove and tag the vacuum hoses and electrical plugs. Disconnect the accelerator linkage (and cruise control linkage, if so equipped) from the throttle housing. Disconnect the throttle position sensor harness.
Disconnect the coolant hoses from the throttle housing.
Working from the rear of the manifold, disconnect the vacuum lines and the electrical harness. Tag the connectors and lines for ease of assembly.
Detach the fuel injector electrical connections. Disconnect the injector harness loom from the manifold and pull out of the way.
Disconnect the fuel lines from the injector rail.
Disconnect the intake manifold support from the valve cover. Remove the nuts holding the intake manifold and remove the intake manifold.
Install the intake manifold on new gaskets and torque the nuts to 16-18 ft. lbs. (22-25 Nm). Install the support and torque to 15-17 ft. lbs. (20-24 Nm).
Install the fuel lines to the fuel rail. Install the injector harness loom and connect the fuel injector plugs.
Connect all lines, electrical connections and harness connections. Connect the coolant lines, the throttle position sensor and the throttle cables.
Connect the ducting from the air flow sensor to the throttle and the air flow sensor.
Fill the cooling system with coolant mixture and connect the negative battery terminal.
Disconnect the battery ground cable. Remove the air duct to the throttle body.
Disconnect the rear mounting bracket and remove the hose.
Loosen the front mounting bracket and remove the nut directly under the throttle body.
Remove the 9 mounting bolts and lift off the upper manifold section. Pull the hose off the fuel pressure regulator at the same time.
Pull the plug plate off the fuel injectors and remove the clamp.
Remove the injector rail with the fuel injectors attached. Remove the 5 bolts holding the lower manifold section and remove the manifold.
Fig. The rear brace and hose on the M42 engines intake manifold
Fig. Remove the this nut when removing the upper section of the M42 engine's intake manifold
Fig. Remove the these bolts when removing the upper section of the intake manifold-M42 engines
Fig. Lift off the upper section of the intake manifold and remove the vacuum hose-M42 engine
Fig. Replace the gasket and check the dowel sleeves before replacing the upper section of the intake manifold-M42 engine
Fig. Removing the injector rail-M42 engine
Fig. Remove these bolts to remove the lower intake manifold-M42 engine
Check the sleeves on the studs. Replace the manifold gasket and install the lower manifold section. Torque to 10-12 ft. lbs. (13-17 Nm).
Lubricate the injector seals with a slight film of oil and install the injector rail. Install the plug plate and clamp.
Connect the fuel pressure regulator vacuum line and install the upper manifold section with a new gasket. Torque to 10-12 ft. lbs. (13-17 Nm).
Tighten the nut directly under the throttle body. It may be necessary to bend the tab against the throttle body.
Connect the front and rear braces. Connect the hose to manifold. Connect the air duct to the throttle body. Connect the negative battery terminal.
A Torx® nut driver is needed to perform this operation.
Disconnect the negative battery cable. Remove the cap nuts at the outer ends of the 4 throttle necks. Then remove the mounting nuts underneath.
Make sure the engine has cooled off. Loosen the hose clamps for the air intake lines and for the fuel lines where they connect with a the injection pipe. Collect fuel in a metal container.
Disconnect the throttle cable.
Pull off the intake manifold. Cut off the crankcase ventilation hose running to it from the crankcase. Then, remove the manifold and place it aside. Supply a new crankcase ventilation hose.
Pull off the throttle valve switch plug. Carefully pull the injector plug plate evenly off all 4 injectors.
Pull the fuel pressure regulator vacuum hose off the pressure regulator.
Remove the 2 mounting bolts for the injector pipe. Then, carefully lift off the pipe and injectors.
Unscrew the nut attaching the ball joint at the end of the throttle actuating rod to the throttle linkage. Supply a new self-locking nut.
Remove the nuts attaching the throttle necks to the cylinder head. Then, remove the 4 throttle necks as an assembly.
Separate the throttle neck assemblies by pulling them apart at the connecting pipe.
Inspect the O-rings in the connecting pipe and at the outer ends of the throttle necks. Replace as necessary.
Reverse the removal procedure to install. Use the new throttle linkage self-locking nut and the new crankcase ventilation hose.
Torque the nuts attaching the throttle necks to the head and the intake manifold to the throttle necks to 5-8 ft. lbs. (9-11 Nm). Adjust the throttle cable.
For more car related problem troubleshooting:---
This are the sections, you can go through and click the link to read its troubleshooting.