i had a used engine put in my car its got 44,000 miles on it runs great other than sometimes it idels real low and when i give it gas it wont go until it catches up does it mostly when its cold but sometimes when it warm it like jerks when i give it gas

 

have you checked your air filter? I'd check that and change if need be, then seafoam it, change plugs and then run some fuel system cleaner. If that doesn't work clean your EGR valve. Are you getting a CEL?

 

iacv, clean or replace.

 

Maybe it's the idle control valve, but not necessarily. If the idle is just low it could be poor air intake. If the idle is bouncing up and down at idle then it's almost 100% the IAC valve.

 

Clean the intake idle contol valve on the throttle body.

 

If its idling low and with your symptoms it may be a IACV (clean like the others stated) it may also be the TPS (throttle position sensor) Clean your throttle body out and clean the IACV and see if that helps. Run some seafoam or fuel injector cleaner thru your fuel system as well