Chevrolet Repair: start-up question, coolant temp, mixture control

Question
QUESTION: Wayne,

I know this forum is for Chevy but I figured you would be able to answer this question related to a 1999 Ford Taurus SE with 82,000 miles.  Recently, when the car sits for 30-60 minutes after running (engine is warm/hot) and then I restart it, it sputters and wants to stall.  I have to hit the accelerator to get it over 1000 rpm and then it is fine.  The car runs great and it doesn't do this all the time, only intermittenly.  Any ideas what could be causing this?  Thanks for your help.

ANSWER: Hey,

 It could be something causing it to load up with fuel.  The best stragey is to start with the basics and check a spark plug and the ignition wires.  Once the basics are out of the way someone should access the data stream and check the fuel trims.  It sounds like it may be commanding an incorrect fuel ratio that is not rich enough when you first start it up.

Wayne


---------- FOLLOW-UP ----------

QUESTION: Wayne,

My car did the same thing again today and I would like to get it checked out at the next oil change.  How does a technician go about checking the data stream and fuel trims?  Just curious.  Thanks.

Answer
He needs to hook up a scanner such as a snapon Mt2500, OTC genysis, MODIS etc.  He should monitor the coolant temp sensor for accuracy and the fuel trims and o2 activity.  Any fuel trim number at idle that is greater than plus 7 percent or less than -7 percent indicates a mixture control problem.  The ECU may be leaning or fattening up the mixture due to a sensor problem or mechanical problem.

Wayne