In March 2020, on my way back from my last flight due to COVID, the car lost significant part of its power and the engine light came in. Only 3 cylinders were operational.
I sent the car to my trusted technicians, who after a compression test, they found a burnt valve caused by a damaged PCV valve.
The engine was properly repaired. New valve, new engine cover with new PCV valve, repair of the cylinder hear, new thermostat housing (leaking), repair of some oil leaks, cleanup etc.
As a result I have now I have no leaks, oil consumption is around 200ml/1000km and the engine is back alive and strong.
However, every day, after a cold start and for 3-4 minutes, the car runs rough. It is not properly idling. After these 3-4 minutes pass, the engine is running smoothly and fine.
Any idea what can this be?
I have done around 4,000kms with this issue and it seems to have improved, but not significantly.
Thanks!

 

Usually with rough starting, it is attributed to a failing high pressure fuel pump. Read the fuel rail pressure to see if it's within spec.

 

Came back.. Issue not resolved (not many miles driven though due to COVID).
Rough start-up. Fuel pressure is in specs (checked with the OBD reader). And the car runs fine after a couple of minutes. This happens only after a cold start at the beginning of the day...
Any ideas?

 

MINIs don't use an idle air control valve; the DME changes valve lift with a servo motor to control the inlet valves and altering the amount of air that is entering the engine; this is how idle speed is controlled on a MINI. If the car runs fine (other than idle), you probably have a problem with the valve lift system. Remember, the DME has limits on how much it can control valve lift, so I'd start with inspection of the throttle body for contamination.

 

Thanks.
If there was an issue with the throttle body, wouldn't this have some impact in the overall driving of the car? After a couple of minutes, the engine works fine..
Any guides/schematics on how to clean the throttle body? In an motorbike i used to have, accessing it was easy and I was cleaning it with brake cleaner...

 

It sounds like we're dealing with an issue that's apparent in only open loop cold start mode. When the DME is running the motor only off of pre determined values. ie. .45v on the upstream o2. However, there are sensors that are used in open loop like the coolant temperature sensor.

After the car has warmed up, it goes into closed loop and will start reading off of the sensors in the car, MAF, O2, etc.

I would look (again) into the HPFP values, real time value vs commanded value. I would also look into how each cylinder is burning, by checking the colour of the spark plugs tips. Could be an issue with one or more fuel injectors. I would also suspect a vacuum leak, however if it is running as poorly as I'm imagining, it would throw lean/rich codes.

The throttle body on these cars is very smart. It would throw a code. Your car having the N14 does not have variable valve lift (valvetronic) and so mkov's comment is invalid.

Disconnect the MAF prior to your next cold start and see if it runs rough. It will throw a CEL. Comment back on what happens.

 

Thanks robjlr,
I took off the MAF. It started even worse than before.
Plugged it in and went back to normal.

I have a couple of videos from "cold" starts, but not sure how to upload them here...

 

@f_p

Right, you can’t upload your videos here. Instead, you will need to upload your videos onto YouTube and then copy the video link to here.