the pi your referring to involves a loose rocker arm with a missing ball or tip causing a misfire,although if a misfire is severe enough the mil will be on,I have not personally ran into this concern so I have no other input
it sounds to me like either you need another dealer or a different tech to work on it,but on the other hand its like going to the doctor and saying I had this pain last week but now its gone please tell me what happened?intermittents are the hardest problems to fix,if indeed you had a loose rocker arm as the bulletin states you would have a distinct clacking in the valvetrain and almost certainly a cel on.any miss thats bad enough to feel trips the cel and alot trip it when customer doesnt even feel it so I doubt rocker arm is your problem.Ive driven several g6's and have not experienced your concern,nor have I experienced it in a malibu z body which carries the same underpinnings as your car.if it does shake at idle with vehicle not in motion then its not tire relatedYes. Went back again on Monday and was supposed to take a tech for a ride then, but they did a surprise shuffle of service departments and were maxxed out to say the least. What didn't help is, somehow, over the weekend it smoothed itself out to have really only a slight bit of a vibe, and that was still the same on Monday.
I still took it in, as there were other issues too, and told them to re-check. Got a call an hour later and they told me--though now thinking I'm nuts--that they drove it 20 miles (sure did...I looked at my gas gauge) and fixed the one thing (gas cap message) but said they felt and heard nothing. Though, to further it, sternly told me again "You MUST NOT put anymore than 30 psi in those tires." I never did, only put them back up to 31 after they dropped them into the 20's the time before, and that has had nothing to do with it other than it wobbling worse with their preferred flat tires.
I like the guys and they try, but something is still really amiss. After that and it being smooth on Monday still, it started back again yesterday and really much so today, until it was an uncomfortable wobble all the way home that anyone would notice. I'm doubting more and more it being anything tire related, as it wouldn't just disappear for 2 days, but just shakes so much it's worrying. Well, and for just now 1003 miles, I should be smiling and not have 5 service receipts.
Engine, transmission, wheels and tires, not sure, but no car--especially not a new one--should be shaking like this. I'm hoping it will continue to enough of an extent for at least the next day I can stop in and grab a tech. At least to soothe the idea that I'm being a nutty new car owner.
That TSB involving a misfire and rocker arms, etc. still also has me worried...especially after my brother commented tonight that it's the exact same shake in the same conditions his old Regal with valve problems has on the road and at idle. Great. But still no CEL and it generally runs fine, so maybe tires...baffled. Don't know.