Pontiac Repair: 96 firebird with P0441 and P0108 ODB codes, emission control system, vacuum hose

Question
Car starts, runs extremely rough for 5-10 seconds, coughs and dies.  ODBii gives P0441 Evap emission control system purge flow fault and P0108 Map/Baro Circuit high input codes.  Help.

Answer
Hi Scott:

the 441 will not cause a roung idle. The 108 for sure will. make sure the vacuum hose to the map sensor is not split or if it's the puch in type to the manifold the seal is not ripped where if goes into the manifold. The hi code can be cause by the sensor it's self or a wiring issue to the sensor. If the sensor had a bad ground going to it it will cause a high code. wigggle the harness around and see if the idle skipps or changes that would be a good indication of a bad connection. the 3 wires going to the sensor are 5V refrence a ground a a signal wire back to the computer. My guess is it's missing a gound to the sensor from the engine computer or a wiring issue to the sensor. Or just the sensor has gone bad.. The other remote possability is the tank pressure sesnor which is also a MAP sensor is bad and it's effecting the engine map sensor. On some of thgw cars they share like ground and 5v refrences. If you have a "fancy" code reader that can actually read the data stream on the engine see if the evap pressure sensor is reading off as well. with the key on and the engine off and the gas cap off the tank sensor should read 0"of H2o for the pressure. If it more than .5 higher or lower then that the sensor is bad in the tank amd possably effectig the engine sensor. Good luck :)