From its very beginnings, the Seville STS represented power, elegance and performance. But the magic didn’t really happen until the 1993 model year, when Cadillac decided to drop in the 4.6-liter, 32-valve Northstar – an exclusive that set the STS trim apart from lesser-optioned Sevilles at the time. Unfortunately, true performance enthusiasts never saw a manual transmission option, which would have taken advantage of the Northstar’s upper power band, while unleashing its exotic, high-rpm exhaust notes. Despite the cramped nature of your vehicle’s engine compartment, replacing the idle air control valve is one of the easiest repairs an owner can do on this otherwise complicated engine.
Ensure the engine has cooled prior to working on the vehicle. Open the hood. Disconnect the wiring connector for the IAC valve, located on the side of the throttle body, behind the “dog bone” engine mount. Note that the top wiring connector connects to the IAC valve, while the bottom connector on the throttle body connects to the throttle position sensor.
Using a Torx bit and bit driver, remove the two screws that secure the IAC valve to the throttle body. Remove the IAC valve. If the valve’s
O-ring did not pull out with the valve, remove it from within the throttle body.
If necessary, roll the supplied O-ring onto the replacement IAC valve. If the O-ring came preinstalled, make sure it’s fully seated within its groove. Lightly coat the O-ring with fresh motor oil. Mount the IAC valve to the throttle body and tighten the screws to 27 inch-pounds, using a torque screwdriver or torque wrench. Connect the electrical connector.
Start the engine. If the engine idles abnormally high, turn off the engine, switch the ignition to the “Off” position and wait for 20 seconds; this will allow the powertrain control module to relearn the pintle position for the IAC valve.
