I recently did a JDM D15b swap in my 91 hatch and after the swap my idle goes up and down when it wants to and at steady throttle it does a weird pulse type thing that kinda sounds like its missing real bad I've gone through my whole ignition system and can't seem to figure it out. No CEL or out of place wires. Please help

 

sounds like the iacv its a common problem with hondas... its on the back of the intake mani its held on with 2 12mm bolts has 2 rubber hoses going to it and a plug... try taking it off and cleaning out the screne on the inside if that doesint work replace it...

good luck

 

I pulled it today and cleaned the screen out. I didn't help but I also noticed a small crack around the plug side up against the metal.

 

bleed your cooling system

 

do you mean for air? If so. How?