Cylinder 2 misfire detected

Meaning of Code P0302

This generic OBD-II code indicates a specific misfire in cylinder 2, detected by the Powertrain Control Module (PCM). A misfire occurs when the air-fuel mixture fails to ignite properly, disrupting engine timing. This code applies to various vehicles (Ford, Toyota, Honda, etc.), but diagnostic steps vary by model.

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Severity

Severe Level:

• Risk of catalytic converter damage and premature engine wear.

• Requires immediate attention to avoid costly repairs.

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Common Symptoms

• Check engine light on (flashing or steady).

• Rough idle or abnormal vibrations.

• Loss of power and hesitant acceleration.

• Gasoline smell or black smoke from the exhaust.

• Increased fuel consumption.

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Possible Causes

1. Ignition Issues:

   • Faulty ignition coil (cylinder 2).

   • Worn, cracked, or fouled spark plug.

   • Damaged spark plug wires or boots.

2. Fuel Problems:

   • Clogged or malfunctioning fuel injector.

   • Insufficient fuel pressure (failed pump or filter).

3. Mechanical Issues:

   • Vacuum leak (cracked hoses, intake gasket).

   • Blocked or dirty EGR system.

   • Low compression (worn rings, faulty valves).

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Diagnostic Procedure

Step 1: Visual and Preliminary Inspection

1. Check ignition components:

   • Inspect cylinder 2’s coil, spark plug, and wires (for oil, coolant, corrosion).

   • Replace spark plugs if maintenance interval is exceeded.

2. Look for vacuum leaks:

   • Use a smoke machine or leak detection spray around the intake manifold.

Step 2: Testing Ignition and Fuel Systems

1. Spark test:

   • Disconnect cylinder 2’s coil and observe the spark (should be blue and strong).

   • Compare with a functioning coil.

2. Injector test:

   • Use a mechanical stethoscope to listen for injector clicking.

   • Measure injector resistance (typically 10-15 Ω).

Step 3: EGR System Check

• Clean clogged EGR ports (use a decarbonizing agent).

• Test the EGR valve with a diagnostic tool (check opening/closing).

Step 4: Advanced Analysis

1. Use an OBD-II scanner:

   • Read real-time data (misfires, fuel pressure, short/long-term fuel trim).

   • Check for related codes (e.g., P0171: Lean mixture).

2. Compression test:

   • Measure cylinder 2’s compression (a difference >15% from other cylinders indicates a mechanical issue).

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Recommended Solutions

• Replace the faulty ignition coil or spark plug.

• Clean or replace the injector in cylinder 2.

• Repair vacuum leaks (replace hoses or gaskets).

• Update the PCM if technical service bulletins (TSB) recommend it.

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Precautions

• Avoid open sparks: Fuel vapors are flammable.

• Disconnect the battery before any electrical work.

• Use insulated tools when testing coils (dangerous 50,000 V).

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Load Testing Procedure

1. Secure the vehicle (wheel chocks, parking brake).

2. Place the engine in drive (automatic transmission) and hold the brakes.

3. Increase RPM to the identified misfire range.

4. Test the spark and observe engine behavior.