Had battery disconnected on 2004 Envoy, 4.2L. after reconnection, vehicle idled rough and nearly stalled when a/c kicked on. forum stated that throttle body needed to relearn after being disconnected but could also be dirty. cleaned throttle body and reassembled. now even worse. check engine light and reduced power light are now on. everything worked fine before I disconnected battery so I don't think there is actually anything bad. what do I do?