I smoke tested my truck in class for a lab i had to do and I noticed the vapor management valve (VMV) was leaking. part of it is about 3.6" in diameter and it is leaking where the two halves snap together.

since this valve lets intake vacuum draw in fuel vapor, is the VMV leaking also causing an engine vacuum leak? im not sure if this "diaphragm" looking thing is on the intake vacuum side or evap side of the valve.

 

bumpin it now that people are awake :)

 

Possible but with it leakin you are actually gettin worse gas mileage by not usin the vapors in the canister

 

The amount of fuel vapor compared to the amount of fresh air the engine is using is so small, i dont think it would have any impact if any at all on fuel economy.

when i look at my short term and long term fuel trim percentages, they are both adding fuel, to me that suggests a vacuum leak

 

well, i ordered a VMV today because when i looked at LTFT and SHRTFT again they were positive, and the idle seemed to change when i put propane by it. didnt have much time to diag today

 

So i replaced the VMV today and recorded my SHRTFT and LTFT and watched my -2 sensors before and after. after the replacement the IAC duty cycle went up and the LTFT and SHRTFT went down significantly. maybe it is mental but it feels slightly stronger now and the idle is nicer.