I have a 1987 firebird with an LG4 and am getting these codes. At first I thought it was the vacuum line. I hooked it back up and it ran much better b/c the vacuum leak was gone. After driving it for a couple of days it was bogging again. When I tested for voltage it stays at 4.1 volts with and without vacuum hooked to it. Does this mean the MAP sensor is bad? It is carbureted so I guess its called a differential pressure sensor or something like that....

 

It's a manifold absolute pressure sensor. Assuming you were checking the proper one (the barometric sensor is the same part, nothing connected to it but wires).

 

Well I just changed the MAP sensor out and that isnt it. But no codes yet. Assuming I get the same codes again I guess the O2 sensor is bad. Could it be anything else? Thanks for the reply.