no chevelle was ever made in 87.
The MAP sensor on a 1987 Chevy Celebrity is mounted to the firewall near the right fender.
the oxygen sensor is in the exhaust manifolds, there should be one for each side
The knock sensor is on the left side of the block below the exhaust manifold.
Camshaft sensors were not used on any of the Chevy Celebrity 2.5L, 2.8L or 3.1L engines
Look near the rear of the transmission on the driver's side.
It is on the side of the throttle body opposite the throttle cable.
It will have two, one in each of the exhaust manifolds.
Passenger side of block just above the starter
They are screwed into the exhaust pipes / system up close to the engine.
As long as the connection is hot with key on or off.
The idle speed is read by the Engine Control Module(computer) and adjusted as necessary by use of the idle air control in conjunction with the throttle position sensor. There is no separate idle sensor as such.
It is located on the throttle body, opposite side of where the throttle cable is attached.