In the exhaust manifolds.
check the O2 sensors
I have a 1996 Firebird and it has 4. Two in the manifolds and one before the catalytic converter and one after.
normally 2
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
The O2 sensor is on the drivers side exhaust manifold. When all four exhaust pipes come together from the manifold that area is called the collector. The O2 sensor should be right there. If your looking for this and you get to the catalytic converter you have gone too far.
2. one pre cat and one post cat
There are several O2 sensors on that vehicle and they are all threaded into the exhaust system at various points.
All O2 sensors are located on the exhaust system. Start at the exhaust manifold and work your way backward, and count them.
On a 1998 Pontiac Firebird with a 3.8L engine, there are typically two oxygen (O2) sensors. The first one, known as the upstream or pre-catalytic converter sensor, is located in the exhaust manifold or just before the catalytic converter. The second one, known as the downstream or post-catalytic converter sensor, is positioned after the catalytic converter in the exhaust system. Both sensors are essential for monitoring the exhaust gases and optimizing engine performance.
All O2 sensors are threaded into the exhaust system at various points. Upstream O2 sensors are located before the catalytic converter(s) and downstream O2 sensors are located after the catalytic converter(s).
There are four o2 sensors on a montero sport.