The #4 cylinder on a 4.3 L engine would be the middle one on the passenger side.
Need to know which engine the 02 S10 has.
After the catalytic converter.
The 02 Chevy S10 with a 4 cylinder or a 6 cylinder does not have a timing belt.
try lmctruck.com all S10 2 wheel drives are the same from 82 to 02
It's on the throttle body, opposite side of the throttle cable.
It might be in the diagram of parts and places, if comes with it.
Three altogether. Two upstream and one down stream.
The engine holds 4 and one half qts. of motor oil with filter change.
Could be a plugged fuel filter or a plugged catalytic converter.
Usually a problem in the emission control system i.e. 02 sensor,
the most common failures on a 02 s 10 are front bearings as well as hub assemblies
If it has the 2.2L engine it has two. If it has the 4.3L engine it has three. All O2 sensors are threaded into the exhaust system at various points.