hey guys, i got a 94 ls and when in park it would rev. between 1500 and 2000rpm. do you have any idea what would cause this to happen?

maybe a bad sensor?

 

search IACV (idle air control valve)

 

fast idle valve...

 

check for vac leaks also, they would cause a fluctuating idle also

 

could be TPS also.

 

i got the same problem... i use seafoam to get all that carbon buildup in my cat out the way after that i used a can of WD-40 and a roll of paper towels to clean all the dirt out from the the throttle body! the idle is alot better and the throttle is more response... give it a try it wont hurt!