Been noticing as it gets colder in the mornings that my S4 stumbles a bit right after cold starting it. I'm still stationary, just start it and watch the RPMs hunt a bit. I tried shifting into reverse quickly to activate the backup cam and then going back into park and revving it. I can see puffs of black smoke come out the exhaust. Anyone else's car doing the same thing? When it warms up a bit the black smoke is gone. Just worried about these sticky injectors I keep hearing about...