It is mounted in the exhaust system. Start at the exhaust manifold and work backward toward the catalytic converter. It is more than likely mounted in the exhaust manifold right at the engine. It may also be mounted where the two exhaust pipes come together.
Bank 1: Backside of the engine, mounted in the exhaust manifold, above the exhaust pipe flange Bank 2: Backside of the engine, mounted in the exhaust pipe (below bank 1 sensor) Bank 3: Frontside of the engine, mounted in the exhaust manifold
If I remember correctly the 351 Windsor has a vertically mounted thermostat that is mounted in the end of the intake manifold The 351 Cleveland thermostat is mounted horizontally in the engine block by the distributor
If you look at the engine , from the drivers side of your Explorer , the IAC valve is mounted on the side of the upper " plastic " intake manifold close to the 4.0 L EFI raised lettering on the manifold . It is mounted just above the rectangular shaped DPFE sensor
The way I tell the difference is the engine thermostat location : On the Cleveland it is mounted horizontally by the distributor and on the Windsor the thermostat is mounted vertically in the end of the intake manifold
I is mounted in the exhaust system. Sometimes in the exhaust manifold, sometimes in the exhaust pipe. There are 2 kinds of O2 sensors. Upstream mounted in front of the catalytic converter and Downstream mounted behind the catalytic converter. You may have one or both.
Under hood, driver side, rear engine area, below exhaust manifold, mounted in engine block. Under vehicle, driver side, below engine area, between exhaust manifold and transmission bellhousing, mounted front of oil pressure sending unit.