P0300

What it means

P0300 means the engine control unit has detected random or multiple cylinder misfires on your Audi, where the misfires are not confined to a single cylinder. It sets this when crankshaft speed monitoring shows uneven rotation that points to combustion failures moving between cylinders or affecting several at once. The cause can be ignition, fuel, air metering or mechanical, and it varies by engine.

Symptoms

• Engine management light on, flashing if the misfire is severe
• Rough or unstable idle with vibration
• Hesitation, jerking or loss of power under acceleration
• Hard starting or occasional stalling
• Smell of unburnt fuel from the exhaust
• Increased fuel consumption

Possible causes

• Worn spark plugs or failing ignition coils affecting several cylinderslikely
• Vacuum or intake air leak (split hose, leaking intake manifold seal or crankcase ventilation fault)likely
• Low or weak fuel pressure (tired fuel pump, blocked filter where fitted, faulty regulator or pressure control)possible
• Faulty air mass meter or other sensor giving a wrong reading (throttle position, crankshaft or camshaft sensor)possible
• Incorrect ignition or valve timing, for example a jumped or stretched timing chain or beltpossible
• Faulty or leaking fuel injectors, or poor fuel quality or contaminationpossible
• Mechanical engine problem such as low compression, leaking head gasket or valve damagerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine speed, load, temperature and whether the misfire happened at idle or under load; check for any cylinder-specific misfire codes (P0301 onwards) too.
2. Check for any related fault codes for fuel trim, air mass, camshaft or crankshaft sensors, and look for any published service updates for the specific model and engine.
3. Visually inspect the ignition coils, connectors, wiring, intake hoses and air filter housing for damage, looseness or splits.
4. Inspect the spark plugs for wear, fouling, oil or incorrect type, and swap or test the coils between cylinders to see whether the misfire follows.
5. Check live data for fuel trims and air mass readings; high positive trims at idle that settle at higher revs suggest an air leak, which can be confirmed with a smoke test.
6. Measure fuel pressure against the specification for that engine, as the correct values and method vary by model.
7. Check the misfire counters per cylinder in live data to see whether one cylinder or several are affected, and review injector operation.
8. If the above are fine, carry out a compression or leak-down test and verify the timing position of the camshaft and crankshaft.

How to fix

• Replace the spark plugs, and any failed ignition coils, with the correct specification parts for the engine.
• Repair any intake or vacuum leaks, including hoses, seals and the crankcase ventilation system.
• Restore correct fuel delivery by replacing a faulty pump, filter or pressure regulator, or by cleaning or replacing faulty injectors.
• Replace any failing air mass, throttle, crankshaft or camshaft sensor confirmed by testing.
• Correct the timing fault by renewing the worn timing components and resetting the timing to specification.
• Carry out the necessary mechanical engine repair, such as head gasket or valve work, if the compression tests show a fault.

Can I keep driving?

This code for other makes

• P0300GenericRandom/Multiple Cylinder Misfire Detected

Nearby codes

• P0205AudiFuel injector failure, Powertrain Control Module (PCM) failure, Wiring issue
• P0301AudiWorn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable), Incorrect ignition timing, Vacuum leak(s), Low or weak fuel pressure, Improperly functioning EGR system, Defective Mass Air Flow Sensor, Defective Crankshaft and or Camshaft Sensor, Defective Throttle Position Sensor, Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems)