The throttle body is of the single-barrel side-draft type.
The lower portion of the throttle valve is heated by
engine coolant which is fed from the cylinder head. The
idle adjusting screw which increases/decreases bypass
air and the evaporative emission (EVAP) control
canister port are located on the top of the throttle body.
A throttle valve dashpot is used to slow the throttle
valve as it approaches the closed position.
DIAPHRAGM STOP SCREW
CAUTION: Do not adjust the throttle stop screw.
It is preset at the factory.
1. Start the engine and allow it to reach normal
operating temperature (the cooling fan comes on).
2. Disconnect the vacuum hose (to the EVAP control
canister) from the top of the throttle body; connect
a vacuum gauge to the throttle body.
3. Allow the engine to idle and check that the gauge
indicates no vacuum.
If there is vacuum, check the throttle cable (see
4. Check that vacuum is indicated on the gauge when
the throttle is opened slightly from idle.
If the gauge indicates no vacuum, check the
throttle body port. If the throttle body port is
clogged, clean it with carburetor cleaner.
5. Stop the engine and check that the throttle cable
operates smoothly without binding or sticking.
If there are any abnormalities in the above steps,
Excessive wear or play in the throttle valve
Sticky or binding throttle lever at full close
Clearance between throttle stop screw and
throttle lever at full close position.
Intake Air System
There should be
Throttle Body (cont’d)
THROTTLE STOP SCREW.
Replace the throttle body if there is excessive play in
the throttle valve shaft or if the shaft is binding or