Whenever our vehicle sows or comes to a stop the RPMs will drop and the vehicle will stall. Spark plugs and air filter have been changed. alternator has been changed and the oxygen/fuel mix has been adjusted as well. Question is: what other problems could been causing this issue.
Who told you that they adjusted your “oxygen/fuel mix”? That is a lie as that is impossible. There are many things that could cause your vehicle to stall when you come to a stop. Anything suggested on this forum is a guess. The only real way to find out is to pay a shop to diagnose the problem. I wouldn’t take it back to the shop that adjusted your oxygen/fuel mix though.
Xebadaih is is correct - especially about this “adjustment” of oxygen/fuel mix. Are you sure you didn’t just get a new O2 sensor or something?
Anyway, the top guesses - b/c that is what they are - would involve a vacuum leak (unless the car will idle normally when you first start it up and when you put it in park or neutral), a failing/sticking idle air control valve (IAC) or a torque converter clutch that is stuck on.
Is your check engine light on?
I asked if it was an O2 sensor and they said no. The check engine light is not on. It was at one point when we first got it but we took it to a different mechanic and it hasn’t been on since. I’m not sure what is going on with it. It is also using a lot of fuel at this time.
“I asked if it was an O2 sensor and they said no.”
You asked who if what was an O2 sensor? You aren’t very communicative are you?
Are you going to check out anything mentioned above?
Add coolant temperature sensor and fuel pressure & fuel pressure regulator to the list.
Have someone check for a dirty or defective idle air control valve. This valve allows air into the engine anytime the accelerator is released which allows the engine to idle.