Signs of an incompletely closing throttle valve may include increased crankshaft speed at idle and fuel consumption; when the valve does not open completely, the engine does not develop full power, is not responsive enough, and jerks and dips are observed in its operation when the car is moving. Contamination of the throttle valve with deposits from crankcase gases usually leads to unstable engine operation at idle. The throttle valve drive is electric, controlled by the electronic unit of the engine management system. Qualified personnel and special equipment are required to repair the electric drive. Therefore, in case of these malfunctions, first try to flush the throttle valve (for example, with a solvent or a special carburetor cleaner in an aerosol can). If this does not produce a positive result, replace the throttle assembly.
1. Disconnect the wire from the negative terminal of the battery.
2. Drain the fluid from the engine cooling system (see "Replacing the coolant").
NOTE: If you have some experience, you don't have to drain the coolant. Prepare plugs of the appropriate size and plug the hoses immediately after disconnecting them. The loss of coolant with this method will be insignificant.
3. Loosen the clamp securing the air supply hose to the throttle body pipe and remove the hose from the pipe.
4. Slide the spring retainer of the engine crankcase ventilation hose tip...
5. ...and disconnect the hose from the throttle body fitting.
6. Move the stopper...
7. ...then squeeze the wiring harness connector lock...
8. ...and disconnect the connector from the throttle assembly.
9. Loosen the coolant drain hose clamp...
NOTE: For clarity, the work here and below is shown with the cylinder head removed.
10. ...and disconnect the hose from the intermediate pipe.
11. Squeeze the coolant supply hose tip retainer...
12. ...and disconnect the hose from the throttle body fitting.
NOTE: If you have not drained the cooling system, immediately plug the hoses with pre-prepared plugs or bolts of the appropriate size to prevent fluid loss.
13. Remove the four bolts securing the throttle assembly to the intake manifold...
14. ...remove the throttle assembly...
15. ...and a sealing ring installed under its flange.
NOTE: Replace the throttle body flange O-ring each time the connection is disassembled.
16. If the throttle assembly was not removed for replacement, clean the contaminated throttle assembly with carburetor cleaning fluid.
17. Remove oil and other contaminants from the cavity of the intake pipe.
18. Install the throttle assembly in the reverse order of removal.
(The text of the article was obtained from the website ChevyMan)