rx7 with idle problems

i am looking into buying a 1990 gxl. when at idle the rpms jump bak n forth from 1500 to 2000. i was wondering what other would look to first to find the problem. i was thinking it could b the o2 sensor being covered partially a clogged or a bad tps. anyone have any advice at all let me kno or if u have experienced this problem and fixed it or know of some1 who has.

Bad grounds can cause improper readings at the ecu causing power loss and idle problems ect. Try installing a ground kit.