Here's how to conduct an engine "stress" test for cars with automatic transmission and power steering: With the engine idling, air conditioner turned on full (whether you need it or not), lights on with high beams, radio on, and foot on the brake, put the engine in gear -- automatic transmission only -- and turn the wheel (if equipped with power steering) all the way to the left and right. Everything should continue running smoothly. Listen for screeches or howls in the power steering and feel for smoothness as you turn the wheel. There should be no surges or bouncing.