Ok, the problem with my car is that everytime I try to start it, it will idle really high and then the rpms will quickly drop and it will die. I think the problem is that my friend loosened a nut on the bolt that holds the throttle plates inside the throttle body, and now I can't get it to tighten back down all the way. Is this what could be causing the crappy idle? When I push down on the mechinism to open the throttle plates, it makes a little "click" before the throttle is open, and when I don't depress the mechinism at all, the throttle plates are completly closed.

Also, the car was shaking horribly going up and down my street, and backfires during deceleration. (This may be due to gutted cats however.) Thanks for all the advice in advance!

 

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is that "click" when the ignition is on car not running? or key off?
you have a pick of what nut was loosened? and have you messed with any screws or anything yet to try to fix it?