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Home › Infiniti › 2001 › QX4 4WD › Repair and Diagnosis › Engine Performance › Engine Controls - On-Vehicle Adjustments › Throttle Position Switch, Ignition Timing & Idle Speed › Basic Inspection › Altima

Basic Inspection: Altima

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 - ALTIMA 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.
  1. 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.

  2. Check Fast Idle Cam Function

    Using scan tool, select MODE 1, and ensure engine coolant temperature is 167-185°F (75-85°C). Using feeler gauges, measure clearance between throttle drum and throttle stop. See Fig 1. If clearance is less than.002" (.05 mm), go to step  7. If clearance is.002" (.05 mm) or more, go to next step.

  3. Fast Idle Cam Inspection & Adjustment

    Remove throttle body from engine. Wait at least 3 hours to bring temperature of thermo element to room temperature. Record room temperature, and measure length (L) of thermo element plunger. See Fig 2. If length is within crosshatch area, thermo element is okay. Go to next step. If length is outside of crosshatch area, replace thermo element, and go to next step.
  4. Measure clearance "A" between stopper and throttle adjusting screw. See Fig 3. Check if clearance is within specification. See Fig 4. If length is within specification, go to step  6. If length is not within specification, go to next step.
  5. To adjust clearance, loosen lock nut, and turn screw "S". DO NOT turn throttle adjusting screw. After adjusting clearance "A", tighten lock nut. Go to next step.
  6. Install throttle body. Start engine and warm to normal operating temperature. Ensure clearance exists between fast idle cam and roller. Go to next step.

  7. Check Ignition Timing

    Start engine and warm to normal operating temperature. Turn ignition off. Disconnect TP sensor harness connector. See Fig 5. Start engine. Check ignition timing using a timing light. Ignition timing should be 18-22 degrees BTDC. Adjust ignition timing by turning distributor. Go to next step.

  8. Check Base Idle Speed

    Check idle speed. Base idle speed should be 600-700 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. See Fig 6. Go to next step.

  9. 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. See Fig 7. Insert a.010" (.25 mm) feeler gauge between throttle adjusting screw and stopper.
  10. Check continuity between TP switch terminals No. 5 and 6. See Fig 7. Continuity should exist. Remove.010" (.25 mm) feeler gauge, and insert.014" (.35 mm) feeler gauge. Continuity should not exist. If continuity is as specified, go to step  13. If continuity is not as specified, go to next step.

  11. TP Sensor Idle Position Adjustment

    Ensure engine is at normal operating temperature. Loosen TP sensor bolts. Remove.014" (.35 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.
  12. 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.010" (.25 mm) feeler gauge, and insert.014" (.35 mm) feeler gauge. Ensure continuity does not exist when throttle is closed. Repeat 2 or 3 times. Go to next step.

  13. 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.

  14. Check Target Idle Speed

    Check idle speed. Target 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. See Fig 6. Go to next step.

  15. 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 - ALTIMA article.
Fig 1: Checking Fast Idle Cam Function (Altima)
G00051911Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Fast Idle Cam Thermo Element Adjustment Chart (Altima)
G97J06558Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Measuring Fast Idle Cam Clearance (Altima)
G00010720Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: Identifying Stopper Clearance Specification Tables (Altima)
G00010721Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: Locating TP Sensor Harness Connector (Altima)
G98B01298Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: Locating Idle Speed Adjusting Screw (Altima)
G98A01288Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: Testing Closed Throttle Position Switch (Altima)
G99C51906Courtesy of NISSAN MOTOR CO., U.S.A.
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