2002 Malibu hesitation

[luxcrusr2000]

I have a 2002 with the 3.1 V6. I was pulling a code P0300 (multiple misfires), so first I replaced the fuel filter, then the spark plug wires (one was cracked), then finally all 3 coils. It's improved, but now it's still hesitating only when the engine is warm. The temp gauge is reading normal, however, I checked the coolant and the tank is empty. Could it possibly be the thermostat? Any ideas?

[maxwedge]

Find where the coolant is going first, pressure test the system, look for traces in the oil or milky deposits in the valve covers.