Generally, my experience is that it won't close the valve on COLD startup. I took my EBPV out, but when it was still in my line was plugged and didn't think it was causing any problems (which it really wasn't other than longer warm up times) until I borrowed my buddies truck and heard his "jet engine" at warm up. Almost freaked me out for a minute until I realizeed what it was.
It basically sends the backpressure to the computer so it knows how far it wants to close the valve...at least that is my understanding.
Originally Posted by Rattlesnake18
Make sure you don't snap it off when you put it back on either. That was an expensive mistake I made.
The factory sensor is pretty tough and I didn't have any problems with it the first few times removing it, but the aftermarket one I bought (after mine wasn't working after a good cleaning. It was a good bit cheaper than the dealer part and was brass...that one broke off with hardly any pressure first time installing it. Had to pull the dang plate and drill and tap it again.
I got lucky and they warrantied it for me so just a big PITA. I'm very careful these days...lol.