2005 Cadillac STS engine vibration at idle

Does it change with engine speed, or go away? One way to narrow it somewhat is to remove the serpentine belt to stop accessory rotation. If it goes away, accessories may be at fault. At that point, the crankshaft, and torque converter would be the largest rotating mass. Is there a check engine light on/flashing, this would indicate potential misfire.

Not storing codes because it has CAN makes no sense to me. What are you trying to read codes with? HAs there been any repairs to the engine that may have some relation to this vibration?

If the vibration has been compared to a similar vehicle, and has been determined unacceptable, the next step would be to disconnect the torque converter and remove the belts. If the vibration is still present, that would narrow it down to an engine imbalance. If it goes away, then I would try re-indexing the torque converter first. It has three bolts that hold it to the flexplate. Try another mounting position and see if the vibration changes.

Sorry they did not respond with what fixed it. Unfortunately that happens but we really want people to come back and close the circle so that it will help others (like you) in the future.

However, if we figure out your issue then that will help others in the future.

So let's start with the basics and make sure we don't make any assumptions.

https://www.2carpros.com/articles/vibration-noise

If the engine only vibrates at idle then the most likely cause would be an engine mount or a possible small vacuum leak.

So let's inspect both of these as well.

https://www.2carpros.com/articles/how-a-motor-mount-works

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Once we work through these items we will have a better idea on what to do next so let me know what you find.

Thanks

No problem. That is good info. The fact that there are no performance issues and the vibration goes away points to a mount issue. However, if this is a small vacuum leak then when you raise the RPM and the PCM introduces more fuel, it evens out the air/fuel enough to smooth it out.

Let us know what you find, we will be here when you do.