The 1990-91 Accord and Prelude use a new type of spark plug with a longer tip and shorter lead. When replacing these spark plugs, make sure to use the same (identical) candle type. Cars using this type of spark plug have small emblems on the air filter.
1. Lubricate the spark plug threads with a drop of oil. Screw in the spark plugs by hand and tighten them simply with your fingers. Never attempt the initial installation with a key; try not to overtighten them. For DOHC engines, the use of a key is unavoidable; turn the wrench with extension very gently by hand until the candle is completely screwed in.
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 are light. If an adjustable torque wrench is available, tighten with a torque of no more than 18 Nm.
3. Install the wires to the appropriate spark plugs. Make sure the wires are well connected. You will feel a click when they click into place. Additionally, make sure that each wire is caught in the appropriate grip or holder in the wiring path. These mounting clips prevent certain electrical interference between the lead wires and also make the engine look neat.