how to fix P0302 misfire code on my BMW 3 Series E90/E91

BMW 3 Series E90/E91 (2005-2012)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0302

4 min read

609 words

Problem Statement

The vehicle is displaying a P0302 trouble code, indicating a misfire detected in cylinder 2 of a BMW 3 Series E90/E91.

Error Code

P0302

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before removing components.

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Decreased acceleration or power
•Poor fuel economy
•Increased exhaust emissions

Diagnostic Steps

1
Scan the vehicle with an OBD-II scanner to confirm the P0302 code and check for any additional codes.
2
Inspect the ignition coil and spark plug for cylinder 2 visually for any signs of damage or wear.
3
Check the fuel injector operation in cylinder 2 to ensure it is delivering fuel correctly.
4
Perform a compression test on cylinder 2 to verify that the cylinder is sealing properly.
5
Inspect the wiring and connectors associated with the ignition system and fuel injector for any signs of damage or corrosion.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Torque wrench
•Spark plug socket
•Compression tester
•Multimeter

Parts Required

•Spark plug (specific to BMW E90/E91)
•Ignition coil (specific to BMW E90/E91)
•Fuel injector (if applicable)

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Scan the vehicle with an OBD-II scanner to confirm the P0302 code and check for any additional codes.
2
Inspect the ignition coil and spark plug for cylinder 2 visually for any signs of damage or wear.
3
Check the fuel injector operation in cylinder 2 to ensure it is delivering fuel correctly.
4
Perform a compression test on cylinder 2 to verify that the cylinder is sealing properly.
5
Inspect the wiring and connectors associated with the ignition system and fuel injector for any signs of damage or corrosion.

Solution

1. Preparation

Gather tools and materials, including an OBD-II scanner, socket set, torque wrench, spark plug socket, compression tester, and a multimeter.
Disconnect the vehicle battery to ensure safety while working on electrical components.

2. Replace Spark Plug and Ignition Coil

Remove Engine Cover: Use a socket set to unscrew and remove the engine cover.
Remove Ignition Coil:
- Disconnect the electrical connector from the ignition coil.
- Unbolt the ignition coil using a socket.
- Pull the ignition coil out carefully.
Replace Spark Plug:
- Use a spark plug socket to remove the spark plug from cylinder 2.
- Inspect the old spark plug for wear and carbon buildup.
- Install a new spark plug, ensuring it is gapped to the manufacturer’s specifications (usually around 0.028-0.032 inches).
- Torque the spark plug to the manufacturer’s specification (typically around 18-25 Nm).
Install New Ignition Coil:
- Insert the new ignition coil into cylinder 2 and bolt it in place.
- Reconnect the electrical connector.

3. Test Fuel Injector

Inspect Fuel Injector:
- If the spark plug and ignition coil replacement does not resolve the issue, test the fuel injector.
- Disconnect the fuel injector wiring and use a multimeter to check for proper resistance (should be within the manufacturer’s specifications).
Replace Fuel Injector:
- If faulty, remove the fuel rail to access the injector.
- Replace with a new injector and ensure proper sealing.

4. Perform Compression Test

Conduct Compression Test:
- Reconnect the battery.
- Remove the spark plug from cylinder 2 and install the compression tester.
- Crank the engine and record the compression reading. It should be within the manufacturer’s specified range (usually 140-200 psi).
- If low, investigate potential internal engine issues (e.g., valve problems, head gasket).