For years my 97 1.6L corolla has been idling rough only when in gear. Smooths out immidiately as rpms increase. I have replaced all 4 mounts, looked for vacuum leaks, cleaned throttle body, new plugs, (all used plugs are gray/brown when removed). Replaced both o2 sensors... Started around 60,000 miles, currently at 90,000. No engine codes.