My 94 coupe with an LT1 engine (auto transmission, 51,000 miles) occassionally surges from idle speed (approx 750 rpm) to about 1,300 rpm in hot weather and after it's warmed up. It's intermittant and happens only in warmer weather (say 80s +). Anyone have any idea what might be causing this? I'd like to fix it myself so any help you can give me will be greatly appreciated. Thanks!