How to Replace Intake Manifold Gasket on a Chevy 3.1by Cayden Conor
The intake manifold on the Chevrolet 3.1 engine, which is commonly used in Luminas, is a two-piece manifold. If the upper manifold gasket leaks, it introduces excess air into the engine, causing the engine to run lean, which means it does not have enough fuel and will detonate. The knock sensor will not be able to compensate if the engine is lean enough, and will send a knock sensor code, turning on the check engine light.
Slide the drain pan under the radiator petcock. Open the petcock and allow the coolant to drain. Close the petcock. Unplug the intake air temperature sensor. Loosen the clamp on the throttle body air inlet duct, using the screwdriver. Pull the duct off the air inlet. Remove the throttle and cruise control cables, using the screwdriver. Remove their brackets, using the appropriate socket.
Unplug the throttle positions sensor and the idle air control valve electrical connectors. Remove the camshaft position sensor's wiring harness from the intake manifold -- it should just unclip from the bracket. Unplug the camshaft position sensor and lay the harness out of the way.
Label the spark plug wires, so you know which cylinder to attach them to when you put the vehicle back together. Pull the wires off the spark plugs with your fingers. Loosen the clamp on the thermostat bypass hose on the throttle body, using the screwdriver. Pull the hose off the throttle body.
Unplug the ignition coil wiring. Unbolt the ignition coil bracket, using the appropriate socket, then remove the bracket with the coils attached, as an assembly. Lay them aside, leaving the spark plug wires attached. If you can't move it far enough out of the way, label the plug wires and terminals before removing them.
Unbolt and remove the purge solenoid and the vacuum canister solenoid. Loosen the clamps on the vacuum lines on the upper intake manifold, using the screwdriver. Pull the lines off the upper intake manifold.
Unplug and remove the manifold absolute pressure sensor and exhaust gas recirculation valve, using the appropriate sockets. Remove the alternator brace. Unbolt and remove the upper intake manifold.
Clean the gasket mating surfaces using the plastic scraper and shop rags. Position a gasket onto the lower intake manifold. Position the upper intake manifold on the gasket. Install the bolts and tighten them to 18 foot-pounds of torque, working from the center out, in a crisscross pattern.
Reinstall the EGR vale, alternator brace, vacuum lines and the MAP sensor. Reinstall the coil bracket and coils, purge solenoid and vacuum canister solenoid. Reattach the thermostat bypass pipe onto the throttle body. Reinstall the camshaft sensor wiring harness and plug wires. Plug in the throttle position sensor and idle air valve connectors.
Reinstall the throttle and cruise control cables, and tighten the bolts to 115 inch-pounds of torque. Reinstall the throttle body air inlet duct. Plug in the IAT sensor's electrical connector. Refill the radiator with coolant.