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HOMESERVICE MANUALSAUDI1996A4 BASE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 2.8LCIRCUIT TESTSDTC P0300/16684 - RANDOM MISFIRE DETECTED
1996 Audi A4 Base, Standard

DTC P0300/16684 - Random Misfire Detected

1996 Audi A4 Base, StandardSECTION DTC P0300/16684 - Random Misfire Detected
NOTE: DTC is set when misfiring has been recognized in more than one cylinder. If misfiring rate is low, MIL is lit after 2 successive trips without a preceding cold start with a malfunction occurring. If misfiring rate is high, MIL will immediately start blinking. Damage to 3-way catalyst is possible. Repair malfunction as soon as possible.
  1. If DTC P1250/17658 FUEL LEVEL TOO LOW is also set in memory, this indicates there is less than 3.2 gallons of fuel in tank. Check fuel tank level and fill if necessary. If fuel level is okay, go to next step. If fuel level was low, erase DTC memory and test drive vehicle. If DTC P1250/17658 FUEL LEVEL TOO LOW is not set in memory, go to next step.
  2. If other DTCs are stored, (i.e. fuel injector, HO2S, fuel system, etc.) these stored DTCs may cause misfire. Repair other DTCs as necessary. Erase DTC memory and test drive vehicle. If no other DTCs are stored, go to next step.
  3. If misfiring has been recognized for several or all cylinders, go to step 5). If misfiring has been recognized on 2 cylinders (i.e., 2 and 4, 3 and 5, 1 and 6), go to next step. If misfiring has only been recognized on one cylinder (i.e. 2 or 4, 3 or 5, 1 or 6), check ignition wiring harness, spark plug cables and fuel injectors for cylinder(s) which are faulty. For fuel injector testing, see FUEL INJECTOR TEST in BASIC TESTING article. Repair as necessary. Erase DTC memory and test drive vehicle. If no other DTCs are stored, go to next step.
  4. Inspect ignition coil for affected cylinders. See IGNITION COIL in BASIC TESTING article. Repair as necessary. If vehicle was not repaired, go to next step. If vehicle was repaired, erase DTC memory and test drive vehicle.
  5. Inspect air intake system for a leak. Repair as necessary. If an intake leak was not found, go to next step. If an intake leak was repaired, erase DTC memory and test drive vehicle.
  6. Inspect fuel pump and residual fuel pressure. See FUEL PUMP table. Repair as necessary. If components are okay, go to next step. If a malfunction was repaired, erase DTC memory and test drive vehicle.
    FUEL PUMP PERFORMANCE

    Function Specification
    System Pressure
    With Engine Idling (1) 55-61 psi (3.8-4.2 bar)
    With Engine Idling (Warm) (2) 46-55 (3.2-3.8 bar)
    Residual Pressure
    Engine Cold (3) 32 psi (2.2 bar)
    Engine Hot (3) 44 psi (3.0 bar)
    Fuel Injector/Injection Rate (4) 2.9-3.7 oz. (86-109 ml)
    (1) With fuel pressure regulator vacuum hose disconnected.
    (2) With fuel pressure regulator vacuum hose connected.
    (3) After 10 minutes.
    (4) Per 30 seconds of operation.
  7. Check EGR valve and system components. EGR flow may be too high. Inspect hoses, etc. Repair as necessary. If EGR system is okay, go to next step. If EGR system was repaired, erase DTC memory and test drive vehicle.
  8. Inspect fuel injectors for carbon deposits. Replace as necessary. If fuel injectors are okay, go to next step. If fuel injectors were replaced, erase DTC memory and test drive vehicle.
  9. Inspect intake valves for carbon deposits. Clean as necessary. Erase DTC memory and test drive vehicle.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.