1992 Beretta Stalls/MAP sensor but computer shows fine

Hi

I have a 1992 Chevrolet Beretta that appears to stall after a while, the engine does not work evenly/smoothly and after few minutes it stalls. The computer reports errors 33 and 34 which is the problem with the MAP sensor but then it shows that it is working properly. Does anyone have any suggestions?

both codes 33 and 34 indicate a bad map sensor, or the circuit to it. Code 33 is a generic MAP sensor code, indicating possible wiring, connection, vacuum supply or the MAP itself. Code 34 indicates a low voltage signal from the MAP to the ECM. IF you haven't changed the MAP sensor yet, do so as the codes you are getting are indicating it is the issue.

Low fuel pressure will trigger a code 33.

I had the same problem with my 90 beretta.Codes 33&34 were pointing to the MAP sensor.The engine ran well at start up but would start to idle rough as it warmed up,and sometimes stall at traffic lights.I replaced the MAP sensor,and nothing changed.Also note I was getting about 6mpg less.Assuming you have the 3.1v6 that I have I removed the intake plenum to check the vacuum lines.Sure enough where the two vacuum lines come in through the steel plate that is attached to the plenum they were both cracked.These plastic vacuum lines are very brittle.I probably cracked them when I replaced the valve cover gaskets weeks before.To fix the plastic lines I cut a couple inches out of the plastic to get rid of the cracks,and spliced them out with 5/32 vacuum hose problem fixed.