The 1.5 litre normally aspirated engine has at least 2 ECU updates which are supposed to have fixed the issue. You will need to raise this with the dealer and ensure that they don't fob you off by saying that the type of petrol is the problem as my own 2018 model experienced this issue with both 95 RON and 99 RON petrol. Some owners have had the crank position sensor replaced also.
You know if the engine is working well as when the car has the wrong ECU setting, switching on the A/C will cause the engine to lose a large amount of power. The updated ECU setting allows you to use the A/C and still be able to drive the car normally.
The 1.0 litre turbocharged engine which has a Gasoline Particulate Filter (GPF) installed is noted as having this type of stutter when it is regenerating. The engine is only a 3 cylinder and the GPF causes a timing change in the engine which makes it behave like it is running with one less cylinder. There does not seem to be a solution for this problem and owners have made lots of complaints but this seems to go nowhere as it has been deemed "a characteristic of the vehicle".
OK, the engine should have been checked for all ECU updates as part of the work carried out by the 3rd party import centre located in Bristol Royal docks, however it has been known that sometimes these have been skipped as seen in the recent EV models which did not have either the Dec 2019 BMS update or the Jan 2020 BMS update. The selling dealer assumes that all is well so won't actively spend time doing this as part of the PDI.
An ECU update is known as a service action so this is normally carried out by the dealer as part of the annual service, however some garages have been known to carry out this work out of sync with the service and soak up any costs themselves, MG Motor UK will not pay the servicing agent the cost of the work as it is normally done as above.
This also means that if you take the car to another MG dealer you are likely to have to pay as the other MG dealer won't be able to recoup their costs directly from MG Motor UK.
You are best advised to approach the MG dealer and advise them of the problem and see if they are able to take the car in and have it sitting outside in the cold overnight.
They can then hopefully replicate the issue and advise you of what needs to be done. If there is no error log in the diagnostics for them to work with then they may end up just resetting the adaptions and see if this clears the problems on its own.
If the problem is only happening when cold but magically clears when the engine is warm, it could be that the engine is not measuring something correctly and the car is running too lean. A faulty sensor might need to be replaced.
Unfortunately EU has mandated car manufacturers to remove as much greenhouse gases from their cars and sadly this can sometimes mess up the driving experience, e.g. after when VW were caught out with the Dieselgate scandal, any vehicles which had been modified had symptoms like overall bad running, higher fuel consumption, etc.
I believe it affects both the 1 litre turbo and the 1.5 litre.
I have the 1.5 and mine received the ECU update and correction 3 weeks ago to get rid of the lumpy running. The update alters the fuel/air mixture and allows the car to run as it is designed to, rather than how the EU would like it to under Euro 6D compliance. It is not a silver bullet as it still has to conform to the stated emissions but it is an improvement. The master technician that carried out the work on my car advised that MG are running these as lean as it physically possible as from a design perspective they are not the cleanest engines to start with but suit their main markets such as China, Thailand and Australia. The UK, under the EU, is the strictest market they sell into and as a result the ECU is doing all sorts of trickery to get them compliant.
As Matty said above take it back to dealer and get the ECU update done.
An aquaintance Taxi Driver has now reached the dizzying mileage of 78,000 miles.
Servicing, several sets of tyres and all 4 wheel bearings.
Still looks like new on the outside.
When I said mine was gone, he looked at the Kia sportage I replaced it with and said "Nice"!
A bit shocking to hear that a brand new car is showing signs of rust already.
It might be good to have a post which collates information about what colour the car is, how old it is, if any rust was found and if so, where?
I'll start the ball rolling:
18 plate registered in May...
From another thread, I have noticed that there seems to be a large difference between what is charged for a 1st service between MG approved garages, it might be useful for owners to provide some details of how much it cost them and when the service was carried out.
If servicing ends up markedly...