The spark plug is one of the most important components in the Subaru Forester engine. It controls the flow of electricity from the distributor cap and sends a charge into the cylinder. The spark then ignites the fuel, driving the piston back down for the next revolution. The combustion process in the gas engine cannot complete itself without the spark. If there is a noticeable decline in your engine performance or it seems you are using more gas than normal, it is probably time to change the plugs.
Check the gap on each of the new plugs using a feeler gauge to be sure each one is correct. The proper gap for the 2001 Subaru Forester is 0.031-inch. Disconnect the battery cables, starting with the negative terminal, by loosening the terminal nuts with a wrench. Remove the battery from the Subaru.
Unplug the mass airflow sensor from the duct on the air filter box. Remove the air intake assembly by removing the three bolts using a socket and ratchet. One is at the front of the intake, one at the left side and one on the right side at the bottom. Loosen the clamp on the air intake duct using a flat-head screwdriver and pull the assembly away from the engine.
Disconnect the wire from the ignition coil using a wrench to loosen the nut if your Subaru has a turbo charger. Remove the bolts securing the windshield washer tank to the Subaru using a wrench and move it aside to gain clearance for the No. 4 spark plug at the right, rear corner of the engine. Do not disconnect the hoses on the tank. Disconnect the wires from the windshield washer motor if your vehicle has a turbo charger. Remove the ignition coil from the automobile using a socket and ratchet if it has a turbocharger.
Grasp the boot of the spark plug wire with your hand and pull the boot off the spark plug. Do not pull by grabbing the plug wire itself or you will damage it. Remove the spark plug from the engine using a spark plug socket, extension and ratchet. You may have to use a universal joint for the socket to gain easier access on the plugs at the back of the engine.
Install the plug and torque it to 15 foot-pounds using the torque wrench. Install the wire on the plug and push firmly until you feel it snap on the plug. Repeat the process with the next plug until you have changed them all.
Put the windshield washer reservoir back in place on the right side and install the retaining bolts using a wrench. Connect the wires to the windshield washer motor if your Subaru has a turbocharger. Install the air intake assembly and tighten the bolts with a socket and ratchet. Tighten the duct clamps using a flat-head screwdriver.
Install the ignition coil using a socket and ratchet to tighten the bolts if your Subaru has turbocharger. Connect the electrical wire to the coil and tighten the nut with a wrench. Place the battery in the car and connect the battery terminals. Tighten the terminal nuts with a wrench.
