General Motors introduced the Cadillac Northstar V-8 engine in 1993, inside the Cadillac Allante. General Motors was assisted in the Allante design by Italian car maker Pininfarina, who create exotic cars in Italy. The Northstar V-8 has been an icon in the Cadillac line of engines since its debut. Vehicles like the Allante, Eldorado, Deville, and STS have all been equipped with some version of the Northstar. The Northstar has always been a fuel injected engine, and as with most fuel injected engines, the throttle assembly or throttle body can become dirty over time and require cleaning.
Raise the hood of the Cadillac. Remove the plastic panel that sits directly on top of the engine. Remove the panel mounting bolts with a 3/8-inch drive ratchet and socket. Turn the bolts counterclockwise, until you can remove them by hand. Do not discard the bolts as you will need them to reassemble the engine beauty panel. Removing this cover will give you greater access to the throttle body assembly, at the entrance of the upper intake manifold.
Remove the air filter lid from the air box, using a large flat head screwdriver to loosen the bolts. The bolts are permanently fused to the air box lid, but will separate from the air box. Turn the bolts counterclockwise with the large flat head screwdriver until the air box lid comes free of the air box.
Remove the intake hose from the engine, by loosening the clamp that holds the hose to the engine. Use a 3/8-inch ratchet and socket to loosen the clamp, then pull the air intake hose off of the engine by hand. Remove the small vacuum hose that is positioned about halfway between the engine and air box, on the air intake hose. Simply pull the vacuum tube out by hand. Remove air intake hose completely from the Northstar.
Spray aerosol throttle body cleaner onto a large cotton swab or a white rag. Locate the throttle control lever on the side of the throttle body and depress it with one hand, to access the entire inside of the throttle. Wipe the inside of the throttle body with the cotton swab or white rag in your other hand. The cotton swab or the rag must be white, so you can know when to rotate either piece around for a clean surface. Rotating to a clean surface on the cleaning tool will remove more dirt and debris from the throttle body.
Turn the Northstar engine on and let it idle for a few moments. Step back over in front of the engine compartment and locate the throttle control lever again. Push the throttle control lever to increase the engine RPM's slightly, with one hand. Spray the entire contents of the throttle body cleaner directly into the throttle body with your other hand. If the engine stalls, restart the engine and increase the RPM's even more prior to spraying the throttle cleaner into the engine. This procedure will remove harmful carbons and debris from the engine and force them to burn off.
Turn the Northstar engine off. Reinstall the air intake hose onto the engine. Snug the hose clamp with a 3/8-inch drive ratchet and socket, then turn the clamp 1/4 turn farther. You do not need to torque or over tighten this part, and doing so could damage the intake hose. Reinstall the small vacuum tube by hand, into the middle of the air intake hose. Attach the air filter lid back onto the air filter box, and snug the mounting screws down with a large flat head screwdriver. Turn the ratchet 1/4 turn farther to finish tightening the box lid.
