Ford Repair: 1996 Thunderbird, thunderbird lx, o2 sensors

Question
   I own a '96 Thunderbird LX Sport....I had one of the O2 sensors replaced recently because engine was running rough & check engine light was illuminated. Car ran fine for awhile then began the same rough idle. If car sat for a couple days it shook real bad then stalled....ran somewhat better once warmed. I'm thinking it could be a MAF sensor...EGR valve?

Answer
Steve,  It definitely sounds like an emissions problem.  This is out of my area of expertise.  However, I would take the vehicle to AutoZone and have them run a diagnosis on the check engine light.  By the way, just because it isn't on (the check engine light) doesn't mean there is not a code.  They offer this as a free service.  Depending on the O'Reilly's store in your area, you might be able to have it done there.  This will help you diagnose the problem a little better.  The easiest way to diagnose emissions problems (without a code reader) is to wait until the car starts acting up.  Then start disconnecting the sensors.  If you disconnect the MAF sensor and nothing happens, odds are the sensor is bad.  When you disconnect a sensor, the vehicle should begin to run different.  A MAF sensor will definitely cause the vehicle to run extremely different when it is disconnected.  I wish I could be of more help.  You might ask another one of our experts.  Good luck,   Jason