Throttle Body: Prelude
- Start engine and run at 3000 RPM under no load with transaxle in Park or Neutral, until radiator fan comes on. Allow engine to idle. Disconnect vacuum hose that connects to EVAP canister from top of throttle body. Connect vacuum pump/gauge to throttle body. See Fig 1. With engine idling, vacuum should not be indicated at vacuum gauge. If vacuum is not present, go to next step. If vacuum is present, check throttle cable adjustment. See FUEL SYSTEM in ON-VEHICLE ADJUSTMENTS article.
- With engine at idle, open throttle slightly and check vacuum gauge reading. Vacuum should be indicated. If vacuum is indicated, go to next step. If vacuum is not indicated, check throttle body port for clogging. Clean with carburetor cleaner as necessary and retest.
- Turn engine off. Check throttle cable operation for binding or sticking. If cable operation is okay, go to next step. If cable binds or sticks, operate throttle lever by hand to see if throttle valve and/or shaft are too tight or too loose. Reroute or replace cable/throttle body as necessary and retest. If throttle valve and shaft are okay, go to next step.
- Check for clearance between throttle stop screw and throttle lever with throttle lever fully closed. If any clearance exists, replace throttle body. DO NOT adjust throttle stop screw.
Courtesy of AMERICAN HONDA MOTOR CO., INC.