I have a 2015 Mitsubishi Mirage ES with a CVT, 128,412 miles. I’ve noticed recently that when I start up my vehicle that the RPMs will throb/surge from 800 to 1200 or so until the vehicle is fully warmed up, driven, etc. It doesn’t happen all the time, it’s more of a hit or miss. My thoughts are that it’s either the battery, which is aging, something with the fuel system, or perhaps the car converter. Anyone have similar issues?
Forum member grevster had a similar problem that was solved with some fuel system cleaner. It's important to note that this is not a fuel treatment, but a cleaner such as Techron or as grevster used, Gumout: