My 92'mr2 n/a stalls and idles rough whenever I come to a stop, if I'm at a stop sign or red light the rpms drop and go back up or just shuts down completely, after about 10 mins or so I can stop normally and car wont shut off or stall. the check engine light does not come on. I took it to a mechanic and they told me it was the iac valve. I replaced it and still having the problem, I don't know what it can be. any help would be greatly appreciated.