The 1990-91 Accord and Prelude use a new type of plug with a longer tip and shorter lead-in. When replacing these plugs, make sure the same (identical) type is used. Cars using this type of plug have small emblems on the air cleaner.
1. Lubricate the spark plug threads with a drop of oil. Screw the spark plugs in by hand and tighten them with your fingers only. Never attempt to perform initial installation with a wrench; try not to overtighten them. For DOHC engines, the use of a wrench is unavoidable; turn the wrench with the extension very gently with your hands until the spark plug is fully inserted.
2. When tightening spark plugs with a wrench, do not apply the same force that you would use on a bolt; just screw them in until they stop slightly. If you have a torque wrench with adjustable torque, tighten it with a force of no more than 18 Nm.
3. Install the wires on the appropriate spark plugs. Make sure the wires are connected securely. You will feel a click when they are in place. Also, make sure that each wire is placed in the appropriate clip or holder along the wiring path. These mounting clips prevent certain electrical interference between the lead wires and also help to give the engine a neat appearance.