91 Sentra Stalling

I have a 91 sentra and recently changed the spark plugs and wires. Before I changed them my car would stall often. Since I changed them it is stalling less. If I use high octane gas it seems to run better. If I use regular octane it runs good until it gets below 1/2 tank. Is there a certain gas that I should use or should I investigate a different problem?

The type of gas shouldn't matter unless something is wrong. Start with your fuel filter, but it kinda sounds like your fuel pump. Hopefully not.

firsy check the base idle. if its ok then check the air flow meter voltage when engine is at operating temp. B13's with 1.6 liter engine should not be above 1.1 volts. if its higher, run a separate ground wire from the air flow meter connector, white wire, to any nearby engine ground. then check your voltage reading again and it should be within specs. this is a common stalling problem fix.

Another common stalling problem is the Idle Air Control Valve. Does it stall when you push in the clutch, or when you are driving down the road?

Sorry it's an automatic. It stalls usually shortly after I start it. I can tell when it is going to stall because I can feel the rough idle. If it has run for a while it is pretty smooth. It is worse when it is cold outside. This morning I started it and let it run for about a minute and took off it was perfect.

Well automatics have that problem too, have you ever cleaned your IACV? If not I would do a search for it, its a 10 minute procedure and all you need is a bottle of carb cleaner and Q-tips and paper towels.