On a 1998 Mercury Mountaineer, the oxygen (O2) sensors are located in two main positions: the upstream (pre-catalytic converter) sensors are found on the exhaust manifolds, typically one on each side of the engine, and the downstream (post-catalytic converter) sensors are located after the catalytic converters along the exhaust pipes. To access them, you may need to raise the vehicle for better visibility and reach. Ensure to disconnect the battery before replacing the sensors to avoid any electrical issues.
On the exhaust pipe, lower, possibly near the catalytic converter.
There are a total of ( 4 oxygen sensors ) according to the engine wiring schematic for the 1997 Mercury Mountaineer in my Haynes repair manual ( 2 oxygen sensors are " upstream " sensors used by the PCM to adjust the air / fuel ratio of the engine ) ( 2 oxygen sensors are " downstream " sensors / catalyst monitors )
For a 1997 Mercury Mountaineer ( 5.0 liter V8 ) ( there are a total of 4 oxygen sensors , 2 sensors that are used with the PCM to adjust the fuel ratio that are nearest the engine on both sides , and 2 sensors that are also called catalyst monitors because they are in the exhaust after the catalytic converters ( downstream sensors ) On the passenger side of the engine in a Mercury Mountaineer ( Bank 1 ) Sensor 1 ( upstream sensor ) and Sensor 2 ( downstream sensor ) On the drivers side ( Bank 2 ) Sensor 1 ( upstream sensor ) and Sensor 2 ( downstream sensor )
you have 4 o2 sensors on the 2002 mountaineer. if you get under the car and look at the exhaust pipe where it goes up either side of the engine you will see it bolted into the exhaust, it has wires coming from it. they are the front 2, the rear 2 are about 2 feet farther to the rear (easier to see)
In the exhaust manifolds.
I'm not a mechanic / technician but I noticed in the power distribution box in the engine compartment of a 1997 Mercury Mountaineer that mini - fuse # 11 ( 20 amp ) is for the HEGO system ( heated exhaust gas oxygen ) sensors The PD BOX is " live " - it is recommended to disconnect your battery cables before servicing anything in the PD BOX
normally 2
The oxygen sensor for bank 1 sensor 1 for a 2000 mercury mountaineer is on the cylinder #1 side.
Try replacing the upstream O2 sensor
There are 2 oxygen sensors.
I do not know for sure how many o2 sensors are on your 98 Chevy but i do no they will be mounted in the exaust mainfold(s) my 93 has only one mounted on the driver side manifold
You will find all O2 sensors threaded into the exhaust system at various points.