I have a 94 Miata m45 running on 10 lbs, I just installed an intercooler and now it won't idle but runs great when on the gas, had no problems before the intercooler

 

What kind of fuel management are you using

 

JR powercard

 

If nothing else changed, then I would assume the intercooler added some additional restriction along the intake tract. Since it doesn't sound like you have any means to adjust the IAC, I'd adjust the idle screw on the top passenger side of the throttle body to bring idle up a bit (rotate counter-clockwise until it idles where you want).

 

Is it idling higher? Is the engine lean as per your wideband? If so, vacuum leak.

 

I have no experience with powercard. But as far as I know, you still use the maf sensor correct? With that being said, I bet there is a boost leak between the intake manifold and the outlet on the supercharger. Make yourself a boost leak tester

 

. No boost leak, typical symtom with SC. install dual throttle body will eliminate the idling issue.

 

Or a megasquirt and decent tuning... I have very little idle issues need some more closed loop tweaking to get there. I had SEVERE idle droop issues with my intercooled MP62 setup on powercards. Mostly being I don't think the stock setup could control the 350cc injectors as well. I got decent idle out of a base tune on the megasquirt and slowly learning the tuning required and it is getting it better.

 

Definitely need Hydra or Megasquirt with intercooler. Power card wouldn't work for me when I added mine either. Be sure you have no leaks. My 1st new intercooler had a hole in it courtesy of a rivet on the TDR plate. Made a hell of a noise !!

 

There is too much volume from the IACV to to the intake ports. My m45 already has idle issues without an intercooler. A full stand alone that would let you tune IACV parameter should help.

 

I did this on my setup a couple days ago, made a HUGE difference. Highly recommend anyone with a hotside SC setup to do this.

 

^This