Ford Repair: Ford Taurus 3.8 excessive fuel usage, taurus 3, ford taurus

Question
My wife's '89 Taurus w/3.8 is using excessive fuel and has a heavy black exhaust.  I believe it is the idle control solenoid, how can I check this?  The car's computer has been replaced with very little improvement.

Answer
Hello and thanks for the question...I'll try to help.
I would check a few things:
1. Check the computer system for fault codes and repair what is needed.
2. Check for a bad head gasket.
3. Check the MAP sensor and vacuum line going to the sensor.
4. Check the over all tune up condition of the engine.

Erik