Important: Over extended time and mileage, deposits may accumulate on the back of the throttle valve plate. The source of the deposit is EGR gas. Typically these deposits pose no problem. Occasionally the deposit may accumulate to a point where perceived pedal effort is effected. This procedure should not be performed on vehicles with mileage under 80,450 kilometers (50,000 miles).

1. Remove the air inlet duct and the resonator.

Notice: Do not insert any tools into the throttle body bore in order to avoid damage to the throttle valve plate.

2. Inspect the throttle body bore and the throttle valve plate for deposits. It is necessary to open the throttle valve in order to inspect all surfaces.

Notice: Do not subject a throttle body assembly which contains the following components to an immersion cleaner or a strong solvent:

•	Throttle position (TP) sensor

•	Idle air control (IAC) valve

•	Sealed throttle shaft bearings

The cleaners will damage the electric components or sensors.
The cleaners will damage some of these components that contain seals or O-rings.
Solvents can wash away or break down the grease used on non-serviceable throttle shaft bearings.
Never use a wire brush or scraper to clean the throttle body. A wire brush or sharp tools may damage the throttle body components.
Do not use a cleaner that contains methyl ethyl ketone. This extremely strong solvent may damage components and is not necessary for this type of cleaning.
3. Clean the throttle body bore and the throttle valve plate using a clean shop towel with GM Top Engine Cleaner, P/N 1052626 or AC-Delco Carburetor Tune-Up Conditioner, P/N X66-P, or an equivalent product.
4. Remove and disassemble the throttle body for cleaning if the deposits are excessive. Refer to the following procedures:

•	Throttle Body Assembly Replacement

•	Throttle Position Sensor Replacement

•	Idle Air Control Valve Replacement

5. After disassembly, clean the throttle body using a parts cleaning brush. DO NOT immerse the throttle body in any cleaning solvent.
6. Assemble and install the throttle body if previously done. Refer to the following procedures:

•	Throttle Body Assembly Replacement

•	Throttle Position Sensor Replacement

•	Idle Air Control Valve Replacement

7. Install the air inlet duct and the resonator.