I seen a diagram that showed two O2 sensors one before and after the catalytic and two on the engine .....when I bought the car last month I remember seeing two brand new O2 sensors in the box laying on the seat...today I peaked under the car and didn't see the 2 O2 senors on the exhaust like the diagram...and my car is only getting about 12 MPG ...... I've changed fuel lines and fuel filter, pump and screen had tank cleaned, 8 fuel injectors, oil and filter, air filter, proper tire psi, practiced good acceleration and braking, but no change in MPG at all and I did all these changes in the same week but no change ....my car is rated at 17/23 mpg. ....1995 Oldsmobile Aurora 189,000. Now I already took into consideration losing a few MPG due to age millage and not trusting factory ratings but missing 2 out of four O2 sensors could that be my problem? And how could I fix that if I can't find the wires for the sensors also I can't get ahold of the guy I bought it from::::::Missing O2 Sensors:::::?
do you have a thermostat?heat regulator for the motor? if so and your running around 195 deg.f then you need to start eliminating ideas.you have 2 o2 sensors you stated now if you need to more, youll find the wiring harness for them under there. even if there is no hole for the o2 in the exhaust youll find loose connectors. if you dont you dont need them.your check engine is probably on even with new os sensors. resistance readings are out of bounds cause the unburned carbon, so either engine is in cold loop or it might have a limp mode. in limp mode, something isnt functioning so it goes into like a cold start function running rich. gonna need to get diag.::::::Missing O2 Sensors:::::?
if you replace the sensors. and it happens to be the caytalic converter..you will be wasting your money.but if it ain't your catalic converter. yes replacing the sensors. will help. because you are burning on rich. ( i know i mispelled something) you will have to buy the sencors with wires. that is why they were on the seat.::::::Missing O2 Sensors:::::?
there is only two O2 sensors on the car. One upstream(before cat) and one downstream(after cat or in cat). I'd try changing the thermostat and the engine coolant sensor. if it is running cold- ie; not over 185 degrees- or the sensor is giving a false(colder than actual) reading to the ecm.. fuel economy will be greatly diminished.
