when i stert it it the idle jumps up and down. but stops when im in gear. now when im in gear and stopped it jumps up and down and jurks my car back and forth. anyone have any ideas. im going out of my mind. just replaced the hole exhaust including cat. brakes and lines. altanator car sat for about 6 months

 

Clean the IACV.

Make sure the cooling system is full-- park on level ground, wait until engine is cold, open radiator cap and confirm it is full to the top.

 

what is the iacv. and i think i might have a coolant leak.