will not hold an idle

I have an 87 Iroc with a 305 tpi. Here lately I can't get it to stay on. I have an error code of 34 and if I read it correctly it's tell me that I have high manifold pressure. I don't know what causes that. Any idea's?

Well, according to the diagnostic flow chart i have, ill give you the short hand. You have one of two problems, either the sensor has gone bad, or you have a short to ground somewhere in the circuit. I would replace the sensor and see if the situation is corrected.