i need some opinions on what may be wrong. this just started yesterday, my car has a mean vibration to it kinda like it has a aggresive cam or it may be missing.... could this be the crank pulley gone bad. i'm gonna try change the plugs as i havent changed them for a while. any help would be appreciated. thanks

edit: plugs fixed it, thanks

 

Well since you dont have any other responses. I'll give it a shot. THis sounds exactly like what happened to my RX , twice. It turned out to be a bad coil both times. I don't know about the GS's but the RX's have individual coils for each cylinder. I took a diagnostic reading and read a misfire on a particular cylinder then swapped out the coil and was back on my way. I found several coils for sale on e-bay and other net sites for between $30 and 60.

As I mentioned this was for an RX/ES engine and I'm not too familiar with the GS but it sure sounds similar.