Its not easy. I did it on a 77 Caprice and it took me three days and two broken fingers. Take it to a shop.
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you either did not gap the plugs to spec or you put this wires on wrong
There are four spark plugs on each side of your 1991 Chevrolet engine. The spark plugs will be near the bottom of the engine.
Connections for the water temperature sensor.
check your fuel filter and also your spark plugs.
look for the round silver or chrome cylinder that plugs into the fusebox.
There are a couple of reasons a 1991 Chevrolet Caprice may stall out. The car may need a new distributor cap or the plugs may need changed. A mechanic will be able to determine the causes of the stalling car.
you rotate the engine to get to the rear plugs but the front ones are easy to replace
drain coolant from radiator, remove one of the frost plugs in engine block, install block heater in place of frost plug, refill radiator with coolant.
Frost plugs are fairly thin steel pucks that can rust through if the coolant was not changed regularly. They are fairly inexpensive to replace if you can get to them.
Disconnect the battery, remove the spark plug cables and boot covers, remove and dispose of the old spark plugs. Next, put in the new spark plugs, attach the boot covers and cables and reconnect the battery.
Any Auto Parts Store can provide this information. BTW, the are called Freeze Plugs or Casting Plugs, not Frost Plugs.