I have a 2002 chevy impala burns lots of gas has 98;000 miles on it / I was told

[John]

that the E.G.R valve could be? the reason /what does this valve do

 

[LeAnne]

If the EGR valve is inoperative, your check engine light should be on. The EGR valve recirculates exhaust gasses back into the engine to lower the combustion temperatures to minimize NOX emissions.

There are numerous reasons why a vehicle "burns a lot of gas."
State of tune, restricted air filter, fuel pressure, faulty O2 sensor(s), low tire pressures, sticky brakes, congested city driving or excessive idling and so forth.

 

[REV B]

Hook up an OBD2 scaner and check for a code. A bad EGR wil produce a trouble code. Since it has 98k on it, I would tune it up and also replace all the O2 sensors. Worn O2 sensers will reduce gas mileage.