Ignition/Fuel - Misfire/Runs Rough On Cold Start

SI B12 02 11
Engine Electrical Systems

January 2011
Technical Service

SUBJECT
N55 - Misfire, Rough Running on Cold Start

MODEL
E82, E88, E90, E92, E93, E70, E71, F07, F10 and F25 vehicles with the N55 engine

SITUATION

On low-mileage vehicles (usually during pre-delivery inspection or shortly after customer delivery), the engine runs rough, misfires and starts after a long crank during a cold start. If the engine fails to start up, the spark plugs may be flooded.

Service Engine Soon is illuminated and various misfire faults (e.g., 2EE0, 2EE1, 2EE2, 2EE3, 2EE4, 2EE6, 2EE7, 2EEC, 2EF0, 2EF1, 140001, 140602, etc.) are stored in the DME module.

In most cases, the fault frequency is only one.

CAUSE

Frequent engine starts and shutdowns without normal engine operation (engine warm-up phase not completed) combined with initial low volatility transportation fuel, resulting in a delayed engine start

CORRECTION

Follow the diagnostic procedure below:

1. Reproduce the cold start condition. Perform a vehicle test drive to completely warm up the engine and clean fuel-loaded catalysts. Reproduce the cold start condition after a test drive. If the misfire is reproduced again, then:

2. Drain the fuel tank and lines and replace with a good quality fuel. Reproduce a cold start again. If the engine still misfires on a cold start, then:

3. Inspect the spark plugs for fuel deposits (heat up/clean reinstall or replace if required). If excessive fuel is found on the plugs and inside the combustion chamber, the engine oil needs to be changed.

4. Check for low fuel pressure during a start-up.

NOTE:
E9x, E7x, and E8x vehicles do not have a low-pressure sensor (the ISTA/D diagnostic request will always show a default value of 6 bars). Use a manual pressure gauge to read the low-pressure value (operating pressure needs to be between 5-7.7 bar).

5. Check the residual low-pressure drop (inspect for a leaking injector if the pressure drop is instantaneous). Replace leaking injectors as needed (TC authorization is required).

6. Do NOT replace the HDP High Pressure Fuel Pump if there are no related faults stored in the DME.

Fault codes 11AC02 - "High pressure plausibility, cold start, pressure too low" (on F10, F07, F25 vehicles) or 2BEE (on E82/E88, E90/E92/E93, E70/E71 vehicles) would indicate excessive rail pressure deviation during the catalyst heating phase.

For comprehensive diagnosis of the N55 fuel system, refer to the attachment "N55_Engine_Fuel_System_DFT_01_18_11".

WARRANTY INFORMATION

For information only

ATTACHMENTS








B120211_N55_ENGINE_FUEL_SYSTEM_DFT_01_18_11