Ford Repair: Fuel system, cash flow problem, mobile mechanic

Question
I drive a 1991 Ford Explorer V6 4.0 Automatic tranmission.  My car would not start so I called a mobile mechanic to help me out, he diagnosed the starter as being the problem.  As soon as he replaced it, my check engine lite came on and has been on since. Now my car is barely running, eats up $5 a day in gas, makes this terrible sound when starting & driving and just started stalling out when I slow down or come to a stop.  I have to wait up to 30-45 minutes before it will start again. I'm afraid that one day it will not restart. I normally don't let my problems get this far but I've had a cash flow problem lately. Do you know what the problem could possibly be? Do you anticipate it to be very expensive to repair? Anything you tell me will be greatly appreciated.  Thank you.

Answer
JACKIE

i would bet the mechanic broke the wires to the o2 sensor,which is by the starter.when your 02 sensor is not working it will not let the car into closed loop,which will cause the car to eat major gas,and cause the car to hesitate,and not want to go.hope this helps.

ken