the last week or so my car has been pretty rough on cold starts. the engine stumbles for a sec then catches and idles. definitely is ruining the start up growl. the only change i have made in the last 2 weeks is switching to premium fuel (93, 92 octane fillups) for the summer. would that cause this?

 

Ugh what do you think this is... a forum for anything other than paranoid 2011 hold conspiracy theories or "should i buy x or a 2011 gt/v6" topics?

 

i know, i should have known better than to try to draw on the experiences of other owners in public forum setting. i mean why would anyone want to do that...

 

The first thing I would check is your vacuum lines. If those are good, check the EGR valve or the idle air controller. But, since you are under warranty, take it to the dealer and let them fix it.

 

BINGO!!!

 

NO check-engine light?

Taking it to the dealer might yield nothing more than, "we couldn't duplicate the problem."

But yeah, if it's under warranty I wouldn't even screw with it. Just take it in.

How many miles do you have on it? Air filter clean? That 93 octane could have been "bad" gas regardless of the octane. Try putting some of whatever you used to put in it again. Shake well. Start over.

 

It's hard to find good service. That's why I do as much as I can myself. On my Corvette's last trip to the dealership, I ended up with a pair of pliers left under the hood. I like free tools, but not in my engine bay.

 

Since the engine would warm up by the time you got there, maybe take a vid of a cold start and show the service writer?

 

hmm thats a creative solution... not a bad idea, if changing gas doesnt fix it ill try that. the warm starts are fine so they probably wouldnt be able to duplicate it.