I have a 2011 HHR with 113000 miles. The whole car vibrates just like a vibrator when in park, idling. It vibrates so bad the back panel on the inside of my hatchback door rattles soo loud. I can feel it when driving and stopped at red lights. It seems to sbside some while driving. Vibration gets worse when running the heater and air conditioning. Its got to be engine related because it happens when the car is stationary. Car has never been tuned up as far as I know. Could it be a timing problem?? I am planning a spark plug change because Im pretty sure they are the original plugs. What you guys think.?

 

Did you forget to mention a red CheckEngineLight on the dashboard? If not, look at the motor/transmission mounts.

 

There are no dummy lights on in the dash.LOL

 

Plugs should have been changer at 100k.
When I did mine, 1 plug had an .080 gap.
New ones made a big differance.
Also, check motor mounts.
Inside passenger wheel well is an inspection hole. If you see a bolthead then replace mount.

 

X3 upper engine mount, correct spark plugs, if not replaced at 100,000 miles,AC Delco 41-103 Iridium do not attempt to gap them !

 

Could also be a balance shaft/chain issue.

 

Also loose exhaust conections mani to block, mani to dp, dp to resonator. Try look at muffler hangers.