Questionrecently my 93 caprice (305 200hp) has been getting REALLY bad mileage. i used to be able to get it 29 mpg, but now i can hardly manage 22-23.
i KNOW its not the driving conditions and i just got a tune up. the car doesn't have ANY noticeable performance issues. although it does seem to be idling a little high like my chevelle, i.e it SEEMS to jump harder when i put it in the drive gear than it used to.
so i am thinking that its the 02 sensor or the air/fuel ratio, or maybe my new heater core.
the question is: if it were the 02 sensor or the air/fuel ratio would the check engine light come on? how would i figure out what wrong with my MPGs.
AnswerHi Richard,
1993 was the era when cars were changing over to OBD-II instead of OBD-I. You want to first verify which you have. I would guess OBD-I (old school). The reason is OBD-II many times have multiple O2 sensors. If you have more than one O2, you will then know which OBD you have.
Another thing you want to realize, is many shops will not give O2, or even check as part of a tune up. O2 sensor's job is to regulate air/fuel ratio. If you have two, they compare notes and adjust the ratio accordingly. O2 will not always turn on the check engine light. air/fuel ratio will turn on a light, by way of the O2 doing so, sometimes.
Bad MPG is caused by many things:
dirty air cleaner, vacuum leak at manifold gaskets, vacuum hose broken, bad O2, bad catalytic if you have OBD-II, egr stuck open a little, tune up needed, leaky fuel injector(s).
IF you have a store that is willing to check your codes for free, have them check the O2 activity. Many times they do this, hoping to sell you parts.
I hope this helps.
C J S
