Hello,

          I own a 1999 V6 3.8 Mustang and with a full tank (about 15
gallons) I would normally get around 310 miles. Currently, I'm only
reaching 200 miles with a full tank of gas(also, the service engine
light is on).  I took my car the shop and they said I have an exhaust
leak (something to do with the gaskets).  the mechanic said he will
fix it plus clean the fuel injector(s), change the spark plugs and
cables.  In addition, I asked him to change the oil, oil filter, the
gas filter and a smog check which I need to do.

         To the best of my knowledge, I can visually verify that he
did change the oil and filters, spark plugs and cables. Not sure if he
cleaned the fuel injector(s) or the exhaust but i can tell my car runs
better. But it did not have the punch that i remember when i last gave
it a tune up. He did not perform the smog check because it was 8pm
Monday, i needed my car to go to work in the morning (i had to have my
car for the next day)AND  he said that he needs to drive the car for
30 min. in order for the computer chips to reset in the car. Is this
true?

          So the following morning (Tuesday) the service light came
back on and on Friday night the car was running like sh.t.  Not only
was the service light on but it was flashing my car had little power,
and when my car was on park it was rocking back and forth.  I took it
back the next day and he said a portion of a spark plug cable (or a
different cable) touched a hot spot and shorted out.  I get my car
back, it runs get and with the punch i remember it use to have. but
still no smog check. he gave me the same story, need to run the car
for 30 mins.  Anyways, the next day the service light comes on and
it's still not giving me the maximum mileage after one week of
driving.

           What can cause this mileage problem i have?  Note, that i
have not change the gas type or location where i buy the gas or had my
smog check yet.

Thanks in advance for your opinions.

Best Regards,

R