Idle Speed

Air Trim Screw Channel Cover:

REMEMBER
A change in idle airflow can occur not only at the throttle body, but other areas as well. You should enter the idle speed procedure only after other possible causes in the following areas are eliminated.
^ Contamination within the idle speed control device
^ Lack of fuel system control (excessively rich or lean)
^ Throttle sticking or binding
^ Engine not reaching operating temperature
^ Incorrect ignition timing
^ Incorrect or clogged PCV system
^ Vacuum leaks (intake manifold, vacuum hoses, vacuum reservoirs, power brake booster etc.



VERIFY

^ Transmission is in PARK (A/T), or NEUTRAL (M/T)
^ Parking brake is applied (automatic brake release disconnected, if applicable)
^ Wheels blocked
^ Engine at operating temperature
^ PCV system is OK
^ Heater, A/C, and other accessories OFF
^ Ignition timing is correct as per specification
^ EEC-IV diagnostics have been performed and vehicle malfunction indicated service output codes have been resolved.



STEP 1
With the engine OFF, connect a tachometer, according to manufacturer's instructions. Disconnect the negative (-) terminal of the battery for 5 minutes, then reconnect it.
STEP 2
START the engine and run at 1,500 - 2,000 rpm for two minutes. Goose the accelerator and let the engine return to idle. Lightly depress and release the accelerator, then let engine idle.
STEP 3
If the engine is not idling properly, turn the engine OFF, and disconnect Idle Speed Control Air Bypass Solenoid.
STEP 4
START and RUN the engine at 2500 rpm for 30 seconds then let idle.
STEP 5
With the transmission in PARK (A/T), or NEUTRAL (M/T), adjust throttle plate idle stop screw so the engine idles at 675 rpm.

NOTE: If the idle speed is too slow, shut engine off and make estimated adjustment. Then repeat steps #2 - #4. Do this two or three times until proper idle speed is obtained.

STEP 6
Shut engine off and repeat steps #1 - #3.

NOTE: If engine still does not idle properly or if idle begins "hunting" (speeding up and slowing down), plug evaporative purge hose. If hunting goes away, the throttle plate is open enough to allow canister purge. Re-adjust idle stop screw to close throttle valve slightly and check purge solenoid and throttle position sensor for proper operation and adjustment. For TPS adjustment procedures, refer to COMPUTERIZED ENGINE CONTROLS.