A Northstar engine is a large high-output engine that is commonly installed on Cadillacs but other luxury vehicles have them as well. There are a few different types of Northstar engine and all of them will be different. On the top of the engine will be the distributor cap with the spark plug wire on the top of that and if you can't see the spark plug you can follow the wire down to the plugs. Also you will need a spark plug remover specific to your Northstar engine to properly remove each spark plug.
Open the hood of the vehicle and disconnect the cables from the battery before you proceed. Look on the right and left side of the engine block and locate the spark plugs. On the V8 engine there will be eight spark plugs and on V6 engines there will be six.
Remove the wires that are connected to the tip of each plug one at a time so that you don't mix them up. Remove the spark plugs one at a time using the Northstar tool. Place the thin edge of the spark plug gapper between the pin in the center of the plug and the metal arm over the pin.
Turn the gapper until the metal arm lines up with the gap setting for that specific engine. Insert the new spark plug into the engine and tighten the plug until it is snug using the Northstar tool. Replace the wire to the tip of the spark plug and repeat for all other spark plugs.
