I have a 1993 Park Ave that has recently developed a steady missfire. It starts fine but
idles roughly and doesn't go away with higher revs. I checked the engine trouble code with an Actron tester and reads "31". Tester book says first check the MAP sensor. My Haynes book doesn't even show where its located. It doesn't state whether a 93 has one or not. My Haynes says "31" is the Park/Neutral position selector switch circuit. How would that affect the missfiring? Any help would be appreciated.
LarryGT

The MAP sensor is typically connected to a vacuum line somewhere, after the throttle blades. Look for a vacuum line that goes to a box about 1.25" tall X 3" long X 1/2" deep (guessing off the top of my head here), that is the MAP sensor. Might be on the firewall, but wouldn't surprise me if they stick it somewhere on the intake manifold or something.

-Bob Cunningham