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Top Tip BMW

BMW N57 Diesel engine, rough running from cold


From cold start, the engine runs rough/misfires for a couple of minutes then smooths out. Will not repeat until another cold start. Possible glowplug codes stored.


Fault in glowplug elements and controller, combined with excessive carbon build up creates a smooth running issue.


Connect your Autologic device and carry out a quick test.

If you only have faults for glowplugs, or a glowplug controller fault, then please proceed as follows:

  1. Remove the inlet manifold.
  2. Inspect for carbon build up on the back of the inlet valves and in the inlet ports. Carry out a cylinder head de-coke to remove the excessive carbon deposits. This can be done without removing the head.
  3. Clean/replace the inlet manifold.
  4. Fit genuine glowplugs and controller.
  5. Update the DDE as there is modified software to improve the smooth running and use of the glowplugs from a cold start.