One aspect of a major service (two year of 30K miles) that isn't performed by many auto repair shops or home mechanics is the throttle body service. Although this tip in general applies to all cars, in particular these paragraphs apply to four-cylinder engines, 1976 and later. Symptoms of sluggish running and slow take-off, poor or irregular idle and declining gas mileage may be alleviated or improved by this basic service. The problem is that residue from the intake mixture and backfires gum up the throttle flap. It will not return to its closed idle position easily, or it sticks when opening.

First, remove the intake bellows from the lower side of the throttle body. Next, disconnect any nearby hoses or other components that may restrict you from accessing the throttle body itself. Then remove the throttle body from the intake manifold by removing the three nuts that retain the throttle body to the flange studs. With the throttle body out of the car, remove the plastic idle adjuster assembly from its side. Immerse the throttle body in carburetor cleaner while you disassemble and hand-clean the plastic idle adjuster and replace its rubber sealing O-ring.

When the throttle body has been thoroughly cleaned, rinse and dry the assembly. Remove the nut on the linkage end of the throttle shaft so you can remove the linkage lever, return spring and related parts. Replace the throttle shaft seal. Now, return the linkage parts to the throttle shaft. Check the operation of the throttle: does the flap open and close freely? Reinstall the idle adjuster using a new gasket. Renew the throttle body gasket before fitting the throttle body to the intake manifold.