[val3nross]

Hi everyone,

I am from Singapore. I am driving a 2008 E90 (320i), running N46B20 engine. I recently made a road trip across to Malaysia (travelled roughly 1000km up and down). Ever since I got up to Malaysia, I have had rough idling on cold start. My RPM fluctuates while idling for about 15 seconds upon cold start. Once warmed up, I do not have this issue (even after I have stop/start my engine while engine is warm).

My current mileage is 186,000km and the last major services done was at 137,500km (by previous owner) which includes the following:
- timing chain + L/R rails, tensioner
- piston & ring
- main & conrod bearings
- alternator pulley
- oil pan gasket & filter
- head gasket
- valve seals
- oil pump chain tensioner & timing rail

I suspect it could be misfiring but is it possible to only misfire during cold start? Are there any other possible causes? Need some help and advice to rectify this before it gets serious.

There is an existing coolant leak problem, identified the leak at top hose and replaced it prior to making the trip up, but a new leak occurred again. Planning to get it fixed together with this issue. Last EO + oil filter change was done together with the top hose replacement and currently reaching 2,000km with the new oil. (I change EO every 6,000-8,000km given it is an old car. Engine runs on Liqui Moly Molygen 5W30, pretty smooth even at 8,000km)

Thank you all in advance!