my BMW 3 Series E90/E91 (2005-2012) won't start in cold weather what's wrong

BMW 3 Series E90/E91 (2005-2012)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

4 min read

613 words

Problem Statement

The BMW 3 Series E90/E91 (2005-2012) is experiencing starting issues specifically in cold weather conditions.

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 working on any components connected to the cooling system.

Symptoms

•Engine cranks but does not start
•Check engine light illuminated
•Increased difficulty in starting after prolonged exposure to cold
•Battery warning light may be on
•Rough idle or stalling after starting in cold weather
•Fuel smell around the vehicle

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any issues.
2
Check the battery voltage and condition, ensuring it is adequately charged and not frozen.
3
Inspect the fuel system for adequate fuel pressure and potential fuel line freeze.
4
Test the engine coolant temperature sensor for correct readings.
5
Examine the ignition system components, including spark plugs and coils.
6
Check the air intake system for any obstructions or frozen components.

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
•Multimeter
•Socket set
•Fuel pressure gauge
•Torque wrench

Parts Required

•New battery (if needed)
•Fuel pump (if needed)
•Spark plugs
•Ignition coils (if needed)
•Engine coolant temperature sensor (if needed)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any issues.
2
Check the battery voltage and condition, ensuring it is adequately charged and not frozen.
3
Inspect the fuel system for adequate fuel pressure and potential fuel line freeze.
4
Test the engine coolant temperature sensor for correct readings.
5
Examine the ignition system components, including spark plugs and coils.
6
Check the air intake system for any obstructions or frozen components.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked in a safe area with access to electrical power if needed.

2. Battery Inspection and Replacement

Sub-steps:
1. Disconnect the negative battery terminal.
2. Remove the battery using a socket set (usually 10mm).
3. Test the battery with a multimeter; it should read above 12.6 volts at rest.
4. If the battery is weak or over three years old, replace it with a new battery rated for cold weather.
5. Reinstall the battery and reconnect the terminals (positive first, then negative).

3. Fuel System Check

Sub-steps:
1. Check the fuel pump operation by listening for it to prime when the ignition is turned on.
2. Use a fuel pressure gauge to verify that the fuel pressure is within specification (usually around 50-60 psi).
3. If the fuel pressure is low, inspect the fuel pump and replace if necessary.
4. Consider using a fuel line antifreeze product if fuel line freeze is suspected.

4. Ignition System Inspection

Sub-steps:
1. Remove spark plug wires and inspect the spark plugs for wear or fouling.
2. Replace spark plugs if they are worn (typically NGK or Bosch plugs for BMW).
3. Test ignition coils with an ohmmeter to ensure they are functioning properly.
4. Replace any faulty ignition coils.

5. Engine Coolant Temperature Sensor

Sub-steps:
1. Locate the engine coolant temperature sensor (usually near the thermostat).
2. Disconnect the electrical connector and remove the sensor using a socket.
3. Test the sensor with a multimeter to ensure it provides correct resistance values at different temperatures.
4. Replace the sensor if it is faulty.