so i have a 1991 civic withe a b18a1 block and b18b head,it was int holding idle at first so i replaced the iacv and the one under the throttle body that didnt fix it.it turns out it was the wires for the iavc.now it starts on its own it idles from 2000 to 300.when i drive its okay but when i let off the gas it feathers down super slow.ill down shift and its like im giving it gas please help i need it

 

the gas linkage on ur throttle body might be over tightened when u changed the iavc.. idk if u took it off or not but when i took mine off i messed with the whole manifold

 

you may have a vacuum leak on the fast idle valve you replaced. Or the throttle body, did you replace the gasket?