What are the symptoms of a failed fuel pressure regulator on a 1988 Mercury Cougar with a 3.8L MPI (multi port injection) V6 engine?

Okay I’m shooting from the hip; car runs rough, stalls when coming to a stop, tailpipe is blackened and dark smoke comes out, oil smells like gasoline and gas mileage has dropped.

Pull your spark plugs, unless they are chocolate brown something is wrong. Also check your vacuum lines for gas. If you see that I would suspect the regulator right off.

@Tropical_Willie and @ARE_you_kidding_me Thanks! Ever see a fuel pump work intermittently?

Yes, if the filter in the tank is clogged. My 1987 Ford F-150 had two tanks, it was bought used. It seems the original owner used only the front tank for 16 months, the rear tank got rusty and . . . clogged the filter. The filter in the engine compartment should be replaced too.