Pontiac Repair: 91 Bonneville poor mileage, chevron techron, mass air flow sensor

Question
I have a 91 Bonneville that I inherited from my grandmother and now my son drives it.  It's had several miscellaneous problems before, but nothing I couldn't fix on my own.  It never did get good gas mileage and it stalls occasionally.  But now the mileage is worse, only about 12 mpg.  There are no engine codes, air filter is ok, plugs look fairly decent.  Any ideas?

Answer
Hi Gary:
first off lets start with the stalling issue. When does it stall cruising down the road or at a top light. when it stalls does it spit chug and sputter then stall or is it like someone turned off the key? Your poor milage and stalling may be intertwined. does it misfire at all? you can try this too with the car running use the handle of a screwdriver and "tap" on the Mass air flow sensor. It's attached to the throttle body it's a black platic sensor with a single harness on it with 3 wires.
Spark plugs do wear out so it's not a bad idea to change them. Use only AC Delco plugs that are designed for the car no magic split fire pulsar magic 8 ball plugs just stock ones. It may not be a bad Idea to change the oxygen sensor too those degrade over time and they are cheap enough. Same thing only a Delco sensor. take a look at the PCV valve that too should only be a Delco part. There is a theme here only use Origianl equipment parts for fuel and ignition control.

You can also try a product called Chevron Techron It's an awesome fuel injetor cleaner and works great. just follow the driections on the bottle to the amount of gas the tank holds..

Good luck :)