95 3.8 with working a/c (finally) and 180,000 miles. When cold and in gear I get this engine surge that is quite strong. With the a/c on, the idle seems extremely low just short of dieing.
Once the engine is warm the van seems to run pretty well with or without the a/c on.
Any ideas?

I'd first try taking off the IAC (Idle Air Control) and cleaning it.