2005 Suzuki Reno would not start. It has been running sluggish sometimes almost like it wants to die. But not like last week when it did die everytime you let off the gas had to replace the O2 sensor?=

A tune up. did you do the service on the car.
filters, spark plugs?
did scan it, to see what DTC errors are set? that is required.
and 02 sensor can die at 100,000 miles the design life span. "bosch"
which engine, option.
1.4 L I4 (petrol)
1.6 L I4 (petrol)
1.8 L I4 (petrol)
2.0 L I4 (petrol)
2.0 L I4 (diesel)
we can not help you , unless. engine is stated and country.
www, the world wide web, make it so we can NOT guess any of that.

the ECU/PCM on your car goes to GREAT efforts to prevent stalls.
the top reason for stalls are:
1: never doing the service per listed items in the glove box guide.
2: EGR stuck open. (if your's has one, some dont)
3: lean air fuel mixture, (lots or reasons and tests)
4 gross rich air fuel mixture casing gross misfiring and stalling.

or something worse. there is always that. eg: burned head valves. etc.