Alright, So I’ve been putting a lot of mileage on the firebird recently, and it’s been taking the abuse pretty well. I do have an intermittent Evap code though....Ok, 2 evap codes. P1442 ( Evap system vacuum switch circuit) and P1441 (evap system flow during non-purge). No symptoms that I notice at all, if I clear the codes they may stay away for a few weeks, or a few days, and then return.

Based on the codes it sound like this vacuum switch thing might be sticking open sometimes and causing the system to evacuate itself when it’s not suppose to?

Where/What is the vacuum switch, how can I check it?

Any other Ideas?

Most EVAP codes are caused by overfilling the tank.

The classic round up the # on the pump to the next even# after the pump has shut itself off.

The evap switch is inline with the canister purge solenoid and when there is vacuum applied to it because the purge solenoid is open it tells the pcm that there is flow. With both codes being set together you're pretty safe with your assumption that the switch sticks sometimes. Pull the line off and see if there are any little black specs that fall out. If there is then your charcoal cannister is the source of the problem becuase the charcoal is being sucked out of it and sticking in the switch. I'm not real familiar with the layout on the 3800 f-body but here is a pic of an LT1 which uses the same components http://shbox.com/1/1996_evap.jpg

Thanks guys....Where exactly is this switch located? It's not very clear in the diagram.