Mitsubishi Repair: rough idel; not shifting, mass air flow sensor, mass air flow

Question
94 mits eclispe, manuel
now my mechanic says my mass air flow sensor needs to be replaced, of course this was after replacing the timing belt and front engine seals for the rough idel.  will replacing the sensor correct the shifting and idel and how much am I looking at spending?

Answer
Lawanda,
Typically, if your Mass Airflow Sensor (MAF) sensor was bad, your check engine light would come on.  A new MAF is quite expensive, and I doubt replacing it will even fix your rough idle and shifting problem.  For the most part, your idle speed has very little to do with your shifting.  If your idle became rough after your timing belt was installed, that probably means the mechanic you brought your car to installed the balance belt incorrectly.  The timing belt is actually two belts; one is the regular timing belt and the other is balance belt.  If the balance belt is installed improperly, your car's idle will be very rough.  

If your idle was rough prior to having the belts replaced, your problem could be contributed to a malfunctioning Idle Air Control (IAC) motor.  The IAC is responsible for controlling your idle speed all together.  But replacing the timing belt is critical, especially if you have a 2.0 liter Eclipse.  For the most part, your should have a dealership mechanic make the repair.  They will get it right the first time.  

If you're not going through a dealership, and they insist your MAF is the problem, take your car to the dealership for a second opinion.  An MAF can be very costly, and most likely is unnecessary.  The dealership can give a much more accurate diagnosis.
Good luck!