LEMON Manuals: Even more car manuals for everyone
Home >> Audi >> 1992 >> 80 Base, 2.3 D, Standard >> Repair and Diagnosis >> Engine Performance >> Engine Controls - Adjustments >> Idle Speed & Mixture

Idle Speed & Mixture

NOTE: Mixture adjustment is not a part of normal tune-up procedure and should not be performed unless mixture control unit is replaced or vehicle fails emissions testing.
NOTE: Idle speed is electronically controlled and cannot be adjusted.
  1. Ensure engine is at normal operating temperature. Turn ignition off. Ensure all electrical accessories and cooling fan are off. Remove cap from exhaust probe receptacle, and connect CO meter. Ensure fit is snug to prevent exhaust leaks.
  2. Remove sealing cap from the top of the charcoal canister. See Fig 1 . Remove crankcase housing breather hose, and vent to atmosphere. Crankcase vapors must vent to atmosphere.
  3. Connect Multimeter (US-1119) and Test Adapter (VW-1315A/1) to differential pressure regulator. See Fig 2 . Set scale to 200 milliamps (mA) DC. Start engine, and warm it to normal operating temperature.
    Fig 1: Identifying Breather Hose & "T" Fitting Locations
    G93049Courtesy of AUDI OF AMERICA, INC.
    Fig 2: Checking Engine Settings
    G93045Courtesy of AUDI OF AMERICA, INC.
    NOTE: If injection lines were disconnected or replaced, increase engine speed to 3000 RPM several times, and then allow engine to idle for at least 2 minutes to bleed injectors and lines.
  4. Insert fuse in fuel pump relay. Malfunction indicator light must come on to indicate that ignition is stabilized for testing. Connect timing light, and check ignition timing. See the IGNITION TIMING  table under IGNITION TIMING for timing specifications.
  5. If timing is incorrect, loosen distributor clamp bolt and turn distributor. Remove fuse from fuel pump relay. Increase engine speed to above 2500 RPM, and then allow it to return to idle. Ensure ignition timing fluctuates between 7 and 20 degrees. Tighten distributor clamp bolt.
  6. Check idle speed. Idle RPM must be within specification. See IDLE SPEED & CO LEVEL SPECIFICATIONS  table. If idle speed is not within specification, check air intake system for leaks. Idle speed is electronically controlled and is not adjustable.
    IDLE SPEED & CO LEVEL SPECIFICATIONS

    Application Idle RPM CO Level
    Checking Value 720-860 .3-3.0%
    Adjusting Value 720-860 .6-1.0%
  7. If necessary, check differential pressure regulator current with the oxygen sensor connected. Reading must fluctuate between -4 and 6 mA and CO level must be 0.3-1.2 percent.
    NOTE: If idle speed drops severely when A/C system is turned on, check idle stabilization system.
  8. Disconnect oxygen sensor harness, and check CO content. Reading must be 0.3-3.0 percent by volume. If CO content is outside range, adjust idle mixture. Turn ignition off. Remove rubber boot from mixture control unit.
  9. Punch hole in center of CO adjusting screw plug, and drill a 3/32" hole to a depth of 5/32". DO NOT  drill completely through as adjustment screw will be damaged. Install a 1/8" sheet metal screw, and remove plug using pliers.
    NOTE: DO NOT  accelerate engine with adjusting wrench in place. Remove wrench after each adjustment, and accelerate engine briefly before measuring CO.
  10. Install rubber boot on mixture control unit. Start engine, and run it at idle. Using Adjustment Wrench (P-377), turn adjustment screw clockwise to reduce or counterclockwise to increase CO reading. See Fig 3 . Install new plug in mixture control unit.
Fig 3: Adjusting Idle Mixture & CO Level
G93046Courtesy of AUDI OF AMERICA, INC.
scientia non olet · About LEMON Manuals