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First what is the spec for fuel pressure? This is a critical value, but chevy is pretty poor at getting closer that 10% + or -. Next the easiest way to think about you map sensor is to think that the engine computer just takes several inputs and does basic math. TPS+MAP+Temp+EGR X Block learn = This much fuel. If the engine is cold the computor just run off the calculation. When the engine is hot it adjusts and learns off the o2 sensor and knock sensor. If the vacume signal is low to the MAP it adds fuel. IF the MAP reads high it reduces fuel. If there is a low fuel pressure or low flow problem can be disguised by unplugging the MAP. I actually got a car home this way as the little piece of hose in the tank between the pump and the pipe was split and bypassing into the tank. Unplugging the MAp richened the mixture up untill it would start run and drive at light throttle settings. It sounds like you have a lean condition and the MAp being disconected allows it to run. Figure out your fuel pressure problem then plug your MAP back in and see how it goes. Good Luck |
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