I have a quick question that is mind boggling me. I own a 96 Civic with a 97 GSR swap. OBD2a

Car is started and in neutral, car idles at 1k. When i let go of the brakes and car starts to move(say im on a hill going downward) the idle shoots put to 1500 and sometimes 2k while its still in neutral. There is no surging in the idle whatsoever and no vacuum leaks. Replaced numerous sensors like iacv, tps, pcv.

Soo confused