It sounds like your engine is not getting enough fuel, try checking the fuel filter.
The petcock on a 1989 Chevy Celebrity is at the bottom of the radiator on the drivers side.
The oxygen sensor on a 1989 Chevy Celebrity is located in the rear exhaust manifold on top about the center.
Looking in my factory service manual for a 1989 Chevy Celebrity I found no reference to an accessory relay.
The spark plug gap for your 1989 Chevy Celebrity 2.8 V6 is .045".
The 1989 Chevy Celebrity V6 is rated at 130 hp.
Could be a fuel pump going bad or a clogged fuel filter,
The speed sensor connector is located on top of the transaxle, passenger side. It is next to the end where the CV axle goes into the transaxle.
on the side of the transmission
There is no fuse on the alternator.
The thermostat on a 1989 Chevy Celebrity is located under the water outlet fitting. Follow the upper radiator hose, it will end at the water outlet.
The engine control module "learns" how to set the idle speed. When you disconnect the battery the engine control module loses that memory and it has to be reset. To regain the setting drive the car for several miles at moderate speeds and it is reset.
No Chevy Celebrity ever had a 4.0L engine