GL-350 Injectors etc
 

We just had a weird issue on our 2014 GL-350. 96,000ish km.

It had been behaving oddly - poor shifting, poor fuel economy and very rough sounding engine noise. Then the dreaded CEL.

Took it in for diagnosis, full service and had all filters changed. Dealer tried to upgrade firmware (or software) and it broke the whole car. In dealer's shop for 1 week, MB Germay involved and was told they were writing new code. Finally back. Vehicle still misbehaving and new CEL on.

Took it back to dealer for diagnosis - now told that it needed 2 new injectors. They were replaced. Vehicle now running well.

Has anyone got any thoughts on why this would happen? Of course, its just off warranty. But, this seems like an engine issue - fuel quality? It just doesn't make sense to me and I would appreciate anyone's advanced cognition.

Thanks!