The main air valve on your Saturn inline four engine is called the "throttle body" (TB).Throttle bodies are precision metering devices, so any carbon, varnish or buildup inside can cause a loss of power and poor idle quality, while generally causing your car to act like a jacked-up beater. Throttle body cleaning is a fairly simple procedure, and is a good starter project for those who are new to auto mechanics.
Identify the throttle body, which is located between the plastic air cleaner intake tube and the intake manifold. Remove the clamp that secures the intake tube to the TB, and pull the intake tube free.
Remove the throttle cable by slipping a pen under the cable, working it toward you until the cable comes off. Remove the vacuum plug-in on top of the throttle body. Unplug the wiring harnesses from the throttle position sensor and the idle air control (IAC) valve on the firewall side of the TB.
Remove the two 10 mm head nuts from the exhaust gas recirculation (EGR) bracket on the bottom-left of the TB. Remove the bracket. Remove the two 10 mm bolts that hold the TB to the intake manifold and tap the top of the TB with a screwdriver handle to pop it loose. Remove the TB and set it on a metal work surface.
Remove the two Allen-head bolts that secure the throttle position sensor (TPS) to the TB, and pull the TPS free. Remove the two Allen-head IAC-mounting bolts, and carefully wiggle the IAC out of the throttle body. Be careful---there's a small O-ring between the IAC and the throttle body, and you don't want to damage it.
Spray the back of the TB's throttle plate and the inside of the TB bore with a liberal dose of carb cleaner, and allow it to sit for 10 seconds. Give it another spray, and start scrubbing the area with your paint brush. Keep cleaning until the area looks shiny and clean. Flip the TB over and repeat the procedure on the front.
Open the TB valve and clean around the area where the plate contacts the inside of the bore.
Spray carb cleaner into the L-shaped and rectangular IAC channels, and scrub them with your paint brush until they're free of deposits. If you can see deposits, get rid of them.
Spray the entire area with brake cleaner to remove any deposits left by the carburetor cleaner.
Clean the metal protrusion (called the "pintle") on the IAC valve itself. The pintle is responsible for metering air into your engine at idle, so making sure it's free of deposits is vital to ensuring idle quality.
Reassemble the TB in the reverse order of disassembly, making sure to install the O-ring back onto the IAC before you slip it back into the IAC receiver. Reinstall the TB back onto your intake manifold (using a new TB gasket) in the reverse order of removal.
