My daughter has a 2003 Ford Focus ZX3 that nearly stalls out when the compressor comes on (i.e., for air conditioner in summer or defroster in winter). She's had hundreds of dollars of work done on it, and her mechanic says he doesn't know what's wrong. A/C blows cold, but idle is so low she can't run it for fear engine will stall. Help, please, with some ideas. She's spent a bunch of money already. Timing chain has been replaced and belts have been checked/changed and are good. About 150,000 miles. Thanks for your help.