Andrew Spence

hi guys!

just tracking down some vacuum leaks to get my car to pass smog. Red1 has been going above and beyond, helping me sort out my emissions problem. after putting in the cat he sold me, the only problem is my NOx is too high at 15 mph, hitting about 1000 with the limit being ~800.

so i bought a vacuum tester and went around testing stuff, which was actually really fun. so, the fuel exhaust breather valve doesn't hold vacuum (bad), the control valve does hold vacuum and slowly comes down (which is good i think), and my diverter (BOV) valve doesn't hold vacuum at all.

i'm wondering if anyone can explain what the fuel exhaust breather valve does?

i know it connects first to a temperature switch, and the porsche shop manual says this opens at 60C or so. when it opens, the line from the fuel exhaust breather valve (plastic valve near the fuse box) will be connected to the vacuum fitting underneath the throttle body.

what does this do? why does it open at a certain temperature?

is this a mechanism to add fuel to the intake when the car is cold? what does the vacuum fitting under the throttle body do? where does it go?

does anyone know which vacuum systems are the most critical for emissions?

thanks in advance for any help!
A

xsboost90

im pretty sure that when the car warms up, it circulates the fuel vapors from the tank/filter etc through a carbon filter that lets the tank breath without any actual stinky vapors to escape.

Andrew Spence

aaahhhh. if it's broken, would that explain why the car reeks of gas when i fill it up sometimes?

hmm, but this wouldn't have any effect on emissions, would it.

thanks for the input.