What charcoal are you using? One thing that I found is, if you dump a bag of charcoal in, the smaller pieces will clog the draft holes in the bottom. This happened to me last weekend while low and slow smoking some pork butts. Almost snuffed out completely!
For max heat you need max draft. Pick out medium and large pieces of charcoal and stack them loosely.
Be careful when you lift that lid, it will give an impressive eyebrow singeing fireball once that thing gets rolling! Don't ask me how I know.
I rarely use my ceramic lid. Prefer to have a trickle of smoke come out the top.
