93 pontiac grand am car issues, any ideas what this could be?

[shannon]

It's acting like a car does when it is getting ready to run out of gas. However, my tank is full. It gets bumpy kind of like a person driving a stick that doesn't quite know how to drive a stick. Than every once an a while the engine will rev up like someone just pressed on the gas pedal while I'm stopped and while i'm driving. All of this occurs more when the car is idling at a light. Although it is happening alot it does not happen all the time. I took it to pep boys and they put it on the engine diagnostic machine and said no codes came up. They replaced my water pump and thermostat because my coolant light was on and they say i was leaking coolant. They gave an oil change and a tune up. Tune up only consisted of replacing spark plugs though. They told me they found know drivability problem and that the car was probably overheating. Car was not doing it at the time when i took it to them. it started again a day after I left?

 

[Marie21]

change your fuel filter or fuel lines might be cloged you should be putting fuel cleaner in when you go to feel up when you let your car run low on gas

 

[Andy C]

Sounds like a small vacum leak to me but, when it studders and revs try to notice if any dark smoke comes from the exhaust, if so, it's the oxygen senser or the wire to the senser may be loose. Look for a vacum leak 1st tho.