I donít think itís a vacuum leak though. It sounds more fuel related to me. I would do two Techron treatments (one after the other) and see if it fixes the problem. If it fixes the problem, switch to a top tier brand of gasoline and do a Techron treatment from time to time. I do a Techron treatment every time my tires are rotated and I try to only use top tier brands of fuel such as Shell and Exon.
A rough idle after a cold start may be cause by your fuel injectors just being dirty. When cold, more fuel is required. Once the car warms up, less fuel is needed and the problem will go away.
I would definitely give the Techron treatment a try! If I had your issue, it would be the first thing I would try at least.
View my fuel log 2015 Mirage ES 1.2 automatic: 40.4 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.5 mpg (Imp)
The first 2 cvt's had 300k and 220k kms. The one that made noise had around 60k. This latest one had 130k, it still drove fine but the fluid was black after changing it multiple times and I pulled it off the road when the driver mentioned it would stall when coming to a stop. https://mirageforum.com/forum/showth...-km-80k-miles)
It's not common for them to blow up all the time. There is one common failure I found that's a cheap bearing that fails that takes out the entire transmission. https://mirageforum.com/forum/showth...inside-the-cvt
View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 35.1 mpg (US) ... 14.9 km/L ... 6.7 L/100 km ... 42.1 mpg (Imp)
The engine still surges upon warm-up, but the vehicle otherwise has no problems. Now at 133,000 miles.
"If an engine is not getting enough fuel (this is called ďrunning leanĒ), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge." Sep 10, 2015
Since you ruled out the vacuum leak, .........
A bottle of Techron costs less than $5 @ Walmart.
I really hope itís not the fuel pump. I found some cheap gasoline additives at Dollar Tree, but it hasnít done anything