5-26 FUEL SYSTEM AND THROTTLE BODY THROTTLE VALVE SYNCHRONIZATION Check and adjust the throttle valve synchronization among four cylinders. USE OF DIGITAL VACUUM TESTER Step 1 • Lift and support the fuel tank. (5-3) • Start up the engine and run it in idling condition for warming up. • Stop the warmed-up engine. • Disconnect the IAP sensor coupler 1 and remove the IAP sensor from the air cleaner box. • Disconnect the vacuum hose 2 from each throttle body. • Connect the vacuum tester hose 3 to each vacuum nipple on E the throttle body. L P M A S Step 2 • Remove the air cleaner box. (5-13) • Connect a tachometer and start up the engine. • Bring the engine rpm to 1 150 r/min by the throttle stop screw. • Check the vacuum of the four cylinders and balance the four throttle valves with the balance screw 4.  Avoid dirt drawn into the throttle body while running the engine without air cleaner box cover. Dirt drawn into the engine will damage the internal engine parts. NOTE: * During balancing the throttle valves, always set the engine rpm at 1 150 r/min, using throttle stop screw. * After balancing the four valves, set the idle rpm to 1 150 r/min by the throttle stop screw. * If the above procedures cannot still synchronize the valves, proceed to the next step.