Why has gas mileage decreased on 1997 Saturn SL2
My Saturn actually runs great, after all these years, but recently the check
engine light has been on. I used a OBD11 meter to get codes. Came back
that the MAP senor needed replaced and spark plug #4 was misfiring. Even
with the two indicator codes, the car ran great and got 35 miles to the gallon.
Last month, I bought a new MAP senor and installed it. I've known for some
time now about the #4 spark plug, as oil has been leaking into the plug
chamber, very small leak and you would notice it if the plug was removed,
kinda oily. But now since I've replaced the MAP the gas mileage has
decreased to around 25miles per gal. Anyone know why the gas mileage
decreased?
Also really don't want to tear into the engine to fix the oil in the plug cylinders
at this time, or I would have.
Thanks for the replies...