Toyota Repair: 97 Tercel Vibration, excessive vibration, toyota dealership

Question
When I first bought my Tercel used in 2000, I noticed a vibration.  I took it to the mechanic before leaving and he just adjusted the seat, because it was rattling.  That helped to some extent.  But, the problem worsened over time.  I was aproaching getting close to the warranty expiring and took it in.  They told me the motor mounts were bad (often defective in this model).  But, unfortunately the warranty was void because I was over miles.  I was angry with myself for not taking it in sooner.  So, I just kept driving it.  I was told it wasn't really a safety issue.  Anyway, just this week I took it in (not to a Toyota dealership)and was told only 1 moter mount was bad and that was replaced.  It is better but still vibrating.  It is primarilly vibrating in idle, not noticable that much while driving. The vibration lessens when the ac is on (as it speeds up the idle.  Any idea what is causing this.  My mechanic did not seem to know.  Thanks!  

Answer
It's still a motor mount problem, I need to know which mount was replaced.
Another issue may be that the car had been involved in an accident and the crossmember that has the mounts on it doesn't quite align properly, have it checked to see if it has been involved in an accident and had frame components replaced, this is almost always the case if there is excessive vibration from the engine.