The most common reason for an engine not to start is a lack of fuel. A plugged air filter can cause and engine to idle rough or not idle at all.
i have a 97 cutlass ciera and i want to know how big the gas tank is
Replace headlight switch- dimming rheostat may be loose
Best left to a pro unless you want to decapitate yourself.
You didn't mention what engine...etc. But for the most part you want .05 to 1.0 volt at idle and 4.5 to 5.0 volts at wide open throttle. It should also increase smoothly as you slowly open the throttle. If it skips and jumps around the TPS is bad.
You may want to go to a car parts store, and get a repair manual for your car. They cost about $16.00 Or, go to a Public Library.
The engine would start and run but it may not want to move.
Possible defective fuel pressure regulator.
Could be a bad water pump on the engine or the radiator is getting plugged or not big enough, also you might want to put in a new thermostat.
Did you try checking the idle adjustment screw?
Start from the spark plugs ans its wires. Also you might want to buy special additives for gas system treatment.
idle speed controll or tps throttle sensor
your engine will sound rough while at idle speed and your gas milage will start getting worse. it also might start to backfire and make a little more noise than it normally would.