Prelude L4-2056cc DOHC (1990)
Throttle Body: Testing and Inspection
CAUTION: Do not attempt to adjust the throttle stop screw, it is preset at the factory and cannot be adjusted.
1. Start the engine and warm it up to normal operating temperature (cooling fan comes on).
Vacuum Pump To Throttle Body
2. Disconnect the vacuum hose to the charcoal canister from the throttle body; connect a vacuum pump/gauge to the throttle body.
3. Allow the engine to idle and check that the gauge indicates no vacuum.
4. Check that vacuum is indicated on the gauge when the throttle valve is opened slightly from the idle position.
a. If the gauge indicates no vacuum, check the canister port. If the canister port is clogged, clean it with carburetor cleaner.
5. Stop the engine and check that the throttle cable operates smoothly without binding or sticking.
6. If there are any abnormalities in the above steps, check the following:
a. Excessive wear or play in the throttle valve shaft.
b. Sticky or binding throttle lever at full close position.
Throttle Stop Screw Clearance
c. Clearance between throttle stop screw and throttle lever at full close position.
7. Replace the throttle body if there is excessive play in the throttle valve shaft or if the shaft is binding or sticking.
