Nissan Repair: p0440 & bpt valve, air leaks, freeze data

Question
Hello, I have 1997 nissan P/U 4x4 2.4L been getting code p0440 on second gas cap checked all lines front to back a few times all seems fine the egr valve seems to be ok moves up and down ok almost stalled it a couple times while running moved on to the BPT Valve and did the blow air suck air temp it seemed to be able to suck air with vacuum applied to botton But I made the mistake of not taken of the truck to do the test, But I still think it could be bad all my I/M monitors on scanner will show ok before the mil except the EGR system mon. Last freeze Data rpm 1925 load 8.2% Map sensor 20Kpa cool/temp 176 s/t fuel t/1 0.8% l/t fuel1 2.3% s/t/f/t3 -100.6% l/t/f/t3 -100.6% speed 8mph thanks for any help you could give

Answer
Jeff,

A couple of things here.  First, I would go through the fuel system to make sure there are no air leaks.  I have found the evaporative canister hoses to be the most common place for vapor leaks.  Also, the top of the gas tank where the hoses tend to rot out.  On the EGR portion I would think the valve needs to come off and the passages need to be cleared from the data you are getting.  Use a wire and compressed air to make sure the passages are clear.   Also, if you have not replaced the oxygen sensor I would as it seems like it would be coated since it is ten years old.