Throttle Body: Testing and Inspection

ON VEHICLE CHECK:

1. Check that the throttle linkage moves smoothly.

Checking The Throttle Linkage For Smooth Movement:

2. Check the vacuum at each port:
a. Start the engine
b. Check the vacuum with your finger

Checking Vacuum At Each Port:

c. Refer to the table for proper operation

Throttle Body Vacuum Table:

d. If a problem is found, proceed to INSPECTION OF THROTTLE BODY (OFF VEHICLE) in this article.

INSPECT AIR VALVE OPERATION:

Cold Test (coolant temperature below 176°F (80°C)):

1. Start the engine.
2. Screw the idle speed adjusting screw all the way in.

Idle Speed Adjusting Screw:

3. The engine rpm should drop below normal.
4. If a problem is found replace the Air Valve.
5. Reset idle speed, refer to ADJUSTMENT PROCEDURES.

Warm Test (coolant temperature above 176°F (80°C)):

1. Start the engine.
2. Screw the idle speed adjusting screw all the way in.

Idle Speed Adjusting Screw:

3. The engine should stall.
4. If a problem is found replace the Air Valve.
5. Reset idle speed, refer to ADJUSTMENT PROCEDURES.

INSPECTION OF THROTTLE BODY (OFF VEHICLE):

1. Remove Throttle Body from engine. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES for proper procedure.
2. Using a soft brush and carburetor cleaner, clean the cast parts of the Throttle Body.

CAUTION: Do not allow carburetor cleaner to come in contact with the TPS, as damage will result.

3. Using compressed air, clean all passages and openings.

Cleaning Throttle Body:

4. After cleaning, check that there is no clearance between the throttle stop screw and the throttle lever when the throttle valve is fully closed.

Inspecting Throttle Body:

5. Refer to ADJUSTMENT PROCEDURES in COMPUTERIZED ENGINE CONTROLS and check TPS adjustment.
6. If the throttle valve binds or appears to be bent, replace the Throttle Body.
7. Reinstall the Throttle Body on the engine. Refer to COMPONENT REPLACEMENT AND REPAIR PROCEDURES for proper procedure.