Lit 15 coals in chimney. Put in center of 15lbs of lump.Had 2 1" valves open and cap off of nipple. Hit 260 before I new it. Capped nipple and closed 1 valve. Temp dropped fast to 235. Had to open 1 valve all the way and the other 1/2 way to get temp around 250ish. Temp never would settle in for very long. Would drop to mid 230s and back up 30mins later to 260s. Kept playing with valves all day but would never settle in at one temp. after 5hrs pulled lid of to take bird off and noticed coals had burnt from side where the wide open valve was and didn't burn on the other side. No wind today at all. I have no leaks anywhere. Any ideas? Don't know how to post a pic. I have weber lid and 3 1" intakes with 2 valves.