I just picked my suburban from having my transmission rebuilt and it is idling very rough for the first time. It was not idling rough before I took it in. What could be causing this?

 

What year Suburban?

They may have dislodged a connector of forgot to reconnect something. Is there a "check engine" light?

Also, they probably disconnected the battery for a long time, so its possible the ECM needs to relearn some parameters.

Steve