Replace the idle air solenoid. This sensor controls airflow into the engine to regulate idle speed. You will find the unit around the throttle body. Unplug the electrical connector and remove two or more mounting screws or bolts using a Phillips screwdriver or ratchet and socket.

Unplug the electrical connector to change the EGR solenoid. This unit controls the introduction of exhaust gases back into the engine through a valve. They come in different configurations. Depending on design, vacuum hoses may be attached to the unit or to the assembly if they share the housing with other components. You may find the solenoid on top and to one side of the engine or by the firewall. Unscrew the mounting bolts using a wrench or ratchet and socket, and disconnect the vacuum hoses.

Remove the vacuum hoses and unplug the electrical connector to remove the canister purge solenoid. This solenoid uses vacuum flow to carry fuel vapors from the fuel tank into the engine for burning. This small unit may comes in different configurations. Some are cylindrical in shape and may be located almost anywhere around the engine compartment. Follow the vacuum hoses connected to the back of the throttle body to find the unit. Some purge solenoids may be mounted in place with a bolt while others may be just hanging loose on the engine compartment.

Disconnect the black, negative battery cable when replacing the starter solenoid. This solenoid may be mounted on the starter motor or the fender, inside the engine compartment. Disconnect the battery cables and wires using a wrench or ratchet and socket.

Remove the electrical connector and mounting bolts or nut to replace the fast idle, sensor. The sensor, located around the throttle body, keeps the throttle open during engine operation and closes the plates when the engine is closed.

Raise your car using a floor jack and safely support it on jack stands to replace transmission solenoids. These solenoids change hydraulic pressure to control functions like shift points, reverse and torque converter lockup. To replace the sensors, unplug the electrical connector and remove the mounting hardware using a wrench or ratchet and socket.

Remove the door trim to find and remove door lock solenoids. They are used to lock and unlock doors electronically. Once you remove the trim, you unplug the solenoid and remove the mounting hardware using a wrench or ratchet and socket.