Your best bet is to spend $40 on a Code reader, and pull the code when the Check engine light comes on. Like the Shop tells you, can't do much without the Code. But the could be a Problem since it is not ur car.
What engine do you have? 3.5l V6?
Maybe the Waterpump took a crap, and the Timing Belt jumped. The smell you get from under the hood could be coolants. If the Timing is off by a little, you will feel hesitation on accel.
Check coolant level,
Open the Radiator when coolants are "Warm" (cold enuff where u can grab with Upper Radiator Hose by hand), with Cloths Wrap around ur Hand and Radiator cap, see if it is holding any pressures. Open it, listen for "Hissing noise"
Usually The Check engine light will Store the Code for ur Mechanic even if it goes off, Maybe Some sensor is shorting out the PCM and erasing the Code when the car dies. But still, when that happens, you should be able to pull codes from other Computer that says something like "Lost communication with PCM".
Take it to the Dealership?
Last edited by steak59; 03-21-2011 at 08:46 PM.