Ford: 1996 Ford Taurus GL (3.0 engine), ford taurus gl, port fuel injection

Question
Dear Greg,
    Hope you can help me, as the Ford dealer I'm dealing with is baffled.  My sister in Mass. gave my daughter in college her '96 Taurus (35K miles).  Car has not been driven over 45 mph its entire life.  Has had all required maintenance performed.  Drove it down from Mass. to VA in Nov. without any problem.  Sometimes (not all the time) after driving it a couple of miles, the car starts pinging (especially going up a hill) and loses power.  The Ford dealer put in two new sensors ($471)because the computer said they were bad.  Problem continues to persist.  Two mechanics at the dealership have driven it home (in fact they have put on over 200 miles), and they have experienced the problem.  They now discovered that too much fuel (too rich a mixture) is entering the engine (around the cylinders) causing the engine to starve out.  The dealership doesn't know why too much fuel is entering the engine, and they told me they will continue to work on the problem and try to figure out why this is happening.  Do you have any thoughts on this?  Any light you can shed on this I would be eternally grateful.  Denis Keating  

Answer
hey denis.

this is a good question, and a few thoughts come to mind...

i believe that the mechanics are correct.  a rich mixture of fuel would cause a loss of power and cause the engine to starve.  denis, your car has multi-port fuel injection (AKA sequential fuel injection).  the mechanics may have told you this.  this means that each cylinder has its own fuel injector.  the gas pedal in your car is connected to the throttle valve -- this is the valve that regulates how much air enters the engine.  when you step on the gas pedal, the throttle valve opens up more, letting in more air. the engine control unit (ECU, the computer that controls all of the electronic components on your engine) "sees" the throttle valve open and increases the fuel rate in anticipation of more air entering the engine.  have the mechanics run a check on your ECU.  it may be increasing the fuel rate too much, or not decreasing it when necessary.  this would result in a rich mixture, and cause the same problems you are having.  any car could have an ECU problem regardless of how old it is. this is why i think this might pertain to you.

i hope i helped with this, denis.  best of luck.

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>PS.  The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. this is called the pulse width, and it is controlled by the ECU. the ECU has all sorts of sensors that control things like this.  you should have the mechanics make sure that all sensors in the ECU are working correctly, and that the pulse width of each fuel injector is acceptable.  in extreme conditions, one or more fuel injectors may be unable to withstand the pressure from the fuel pump, and leak excess fuel into the cylinder(s).  in this case, you need to replace the fuel injectors.