For 1990-2009 cars

1. Remove the air cleaner outlet duct.
2. Remove the air inlet screen, if applicable.
3. Inspect the throttle body bore and the throttle valve plate for deposits. You must open the throttle valve in order to inspect all of the surfaces.
4. Clean the throttle body bore and the throttle valve plate using a clean shop towel with GM Top Engine Cleaner, GM P/N 1052626, Canadian P/N 993926 or an equivalent product.
5. If the deposits are excessive, remove and disassemble the throttle body for cleaning. Refer to Throttle Body Assembly Replacement .

After disassembly, clean the throttle body using a parts cleaning brush. DO NOT immerse the throttle body in any cleaning solvent.

6. If you removed and disassembled the throttle body for cleaning, assemble and install the throttle body. Refer to Throttle Body Assembly Replacement .
7. Install the air inlet screen, if applicable.
8. Install the air cleaner outlet duct.