My girl owns a 04 lancer es with a single cam engine and it is running rough and the check engine light came on. I took it to autozone they scanned it and came up with p0401. So i started fumbling around under the hood and this is what i came up with.

Egr valve is staying open and running rough. I disconnect the hose going to the egr and the car runs perfect. So what would be causing the egr to stay open i though maybe the solenoid was causing the problem so i disconnect the sensor and that didn change. I then pinched the lines and the only one that changes anything is the main vacuum feed that comes from the throttle body. i think it was a green tracer on it. they car only has 3x,xxx miles on it. What do you guys think.

P.S. i allready searched and couldnt find anything like this