[Dale_K]

Mine does that too and has since the get-go. On a cold start it's like a sewing maching but on a hot start it's very coarse and unpleasant. My car is a 1.8 with manual trans. I doubt mine is motor mounts because it starts so smoothly when cold. If they were broke I'd expect it to be rough all the time.

I had a theory it might be the dual mass flywheel but that is totally a guess.

I found another thread about this. One guy reports they changed the cam sprocket but I don't know if it's really the same issue.

http://www.cruzetalk.com/forum/25-service-issues/2973-vibration-during-start-up.html

Let me know if you get some kind of answer or fix.

 

[Dale_K]

The 1.8L doesn't have balance shafts.

I didn't know that. But I don't think the issue is a basic lack of supplemental balance devices because the motor feels smooth in general operation on the road or revving at idle. What I notice is a harshness at the moment of start-up. It feels like the entire powertrain is kind of loose. When it's at it's worst, typically in very hot conditions, I get kind of an impact sound from the manual gear shift area. It's funny how smooth it is on a cold start vs how rough it can be on a hot start in hot weather. I had a theory it might be the dual mass flywheel clunking internally but really I'm not any kind of expert and that's only a WAG. I was thinking maybe there's some kind of heavy grease inside the flywheel that maybe becomes sort of liquid when it gets really hot and makes the flywheel assembly respond differently. Like I said, a WAG.