Hi. I am brand new to this forum. I have searched so many places and spoken with many people. this is my issue:

My gas mileage is terrible. I got the code p0440 which I have looked up and got this answer from someone apparently knowledgeable

"This code means evap system is leaking. The most common causes are vent solenoid, fuel cap, or rusted filler neck. You can activate the vent solenoid to make sure you can't blow through it, if you still can blow through it then replace. Next step would be visual inspection of filler tube and evap lines back by canister under rear of vehicle. IF both look good replace fuel cap. If problem still exists you would want to have a smoke test done to see where leak is coming from"

A lot of people say it's the gas cap. I got a new one. Still have same problem and still have check engine light on. Today, while looking under the hood of my 2001 Blazer 4door 4wd 4.3 v6 vortec in the for top right part of the engine compartment I saw a white ****** connector with a loud hissing sound coming from it. I put my finger to it and realized it is a vacuum. Right beside it I saw a small rubber hose that looks like it should be connected to it as it's about the right size but it was corroded and not clean/flat on the end. I cut it back to the point where it was flat and put it onto that white vacuum device which by the way Tee's off towards the engine on another hose. I have asked people and looked up hour long videos on evap emissions trying to understand what this specific hose is for and can't figure it out. I'm hoping that reconnecting it solved the problem and hundreds of dollars at the mechanic. Can anyone provide any advice? I will share a picture

on the left is the vacuum device which tee's off towards the engine compartment and maybe somewhere else. On the right is the corroded hose that was currently disconnected.

 

What you have found is part of the system that supplies vacuum to the actuators of the HVAC system and to the front axle engagement system.

These rotted engine compartment vacuum hoses are unlikely the cause of your emissions error although the leak can mess up your air to fuel ratio. I have a link in my signature file on how to replace them for my 1999 Blazer with the 4-button controlled transfer case.

The emissions system also has components near the gas tank that you can check. Unfortunately I do not know much about them.

 

If you can't control which dash vents the air comes out, it's those hoses. Here's what I did:
https://blazerforum.com/forum/2nd-ge...d-hose-102386/