Please try to comprehend these two questions as discrete enquiries, and
answer BOTH, appropriately.
1a) Does the car keep on running until it runs out of gas, or does it
eventually die on its own?
1b) If the car dies, how long does it take before the car dies?
2) Does the car run the very same way with the key out as it does with the
key in, or does it run differently each way?
sounds like you have excess carbon on the plugs and in the cylinders.
get new plugs installed, then go for a hard fast drive to burn the
carbon out otherwise known as an "italian tuneup". that should cure it.
in the future, don't buy cheap gas, get high end branded gas - it has
more detergent and therefore lower build-up.
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