Note. Use the following procedure to check and adjust throttle position switch, ignition timing and idle speed. Ensure no Diagnostic Trouble Codes (DTCs) exist before performing test. See SELF-DIAGNOSTICS - QUEST article. Ensure transmission is in Park or Neutral, all electrical accessories (headlights, A/C, rear window defogger, cooling fan, etc.) are turned off and steering wheel is in straight-ahead position.
- Check the following: Harness connectors for poor connections. Vacuum hoses for leaks, kinks or misrouting. Wiring for improper connections, pinches and cuts. Repair as necessary. Go to next step.
- Check Fast Idle Cam Function Using scan tool, select MODE 1, and ensure engine coolant temperature is 167-185°F (75-85°C). Inspect fast idle cam position. Center of mark "A" should be aligned with mark "C", and cam follower's lever should not be touching fast idle cam. (Scheme 16) If fast idle cam operates as specified, go to step 5. If fast idle cam does not operate as specified, go to next step.
- Fast Idle Cam Inspection & Adjustment Allow engine to cool until engine coolant temperature is 68-86°F (20-30°C). Inspect fast idle cam position. Center of mark "A" should be aligned with mark "B". (Scheme 16) If fast idle cam position is not as specified, adjust by turning adjusting screw. Go to next step.
- Start engine and warm until engine coolant temperature is 167-185°F (75-85°C). Inspect fast idle cam position. Center of mark "A" should be aligned with mark "C", and cam follower's lever should not be touching fast idle cam. If fast idle cam operates as specified, go to next step. If fast idle cam does not operate as specified, replace thermo element and retest.
- Check Ignition Timing Start engine and warm to normal operating temperature. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 17) Start engine. Check ignition timing using a timing light. Ignition timing should be 13-17 degrees BTDC. Adjust ignition timing by turning distributor. Go to next step.
- Check Base Idle Speed Check idle speed. Base idle speed should be 650-750 RPM with transmission in Park or Neutral. If idle speed is as specified, go to next step. If idle speed is not as specified, adjust by turning idle speed adjusting screw. (Scheme 18) Go to next step.
- Check Closed TP Switch Idle Position Turn ignition off. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect TP switch harness connector. (Scheme 17) Insert a.008" (.20 mm) feeler gauge between throttle adjusting screw and throttle drum as shown in illustration. (Scheme 19)
- Check continuity between TP switch terminals No. 5 and 6. see scheme 15 Continuity should exist. Remove.008" (.20 mm) feeler gauge, and insert.012" (.30 mm) feeler gauge. Continuity should not exist. If continuity is as specified, go to step 11. If continuity is not as specified, go to next step.
- TP Sensor Idle Position Adjustment Ensure engine is at normal operating temperature. Loosen TP sensor bolts. Remove.012" (.30 mm) feeler gauge, and insert.010" (.25 mm) feeler gauge. Open and close throttle. Continuity should not exist while closing throttle. If continuity exists, turn TP sensor body counterclockwise until continuity does not exist.
- Remove.010" (.25 mm) feeler gauge, and insert.008" (.20 mm) feeler gauge. Slowly rotate TP sensor body clockwise until continuity exists, then tighten TP sensor bolts. Ensure continuity exists when throttle is closed and does not exist when throttle is open. Repeat 2 or 3 times. Remove.008" (.20 mm) feeler gauge, and insert.012" (.30 mm) feeler gauge. Ensure continuity does not exist when throttle is closed. Repeat 2 or 3 times. Go to next step.
- Reset TP Sensor Idle Position Memory Remove feeler gauge. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Turn ignition off. Turn ignition on, wait at least 5 seconds, then turn ignition off and wait at least 5 seconds. Repeat 20 times. Go to next step.
- Check Target Idle Speed Check idle speed. Target idle speed should be 700-800 RPM with transmission in Park or Neutral. If idle speed is as specified, go to next step. If idle speed is not as specified, adjust by turning idle speed adjusting screw. (Scheme 18) Go to next step.
- Clear DTC Memory DTCs may be stored in ECM and/or Transmission Control Module (TCM) from performing basic inspection. Clear DTCs from ECM and TCM. See «SELF-DIAGNOSTICS - QUEST»(ref-135810) article.
