Lost 5 mpg???

[Duster]

So long story short I heard a sound which turned out to be a hole in the rubber elbow of my pcv pipe. I think basically it was just rotten and my spongebob filter in the airbox where the crankcase inlet air comes from got dirty enough that the vacuum caused the rotten boot to fail.

I went and got a new pipe from the dealer which ended up being a new part that superceeded my old part. Main difference is just routing. Same diameters and everything. I almost took the boots off the new one to go on the old one but thought maybe they rerouted it for a reason. So I didn't.

So I changed the PCV, installed the pipe and installed a new spongebob filter in the airbox made of a foam filter from briggs and stratton.

Since doing this my MPG has fallen 5 MPG! I am completely puzzled by this.

Anyone else ever experienced anything similar or have suggestions I might not be considering?

Should I change the PCV out again? Disconnect battery to get a reset on the computer? IDK

 

[tommudd]

Any codes popping up ?
If not I'd start with disconnecting the battery, just for Ss&Gs to see what that does
then go from there

how is it rerouted ?

 

[Duster]

Nope, no codes. There were also no codes or symptoms when the hole developed. I just got out and left it running, and when I did I heard a sound that I couldn't determine if it was a jingle sound or a high pitch suction sound. I first kinda thought idler pulley or water pump. But the engine was hot and I didn't want to try to take the belt off to see. So I went looking for vaccum leaks and found it.

The new style PCV pipe just routes from the valve, up over the intake to the other side where it hooks up to the intake. My original one went under the intake. And when I say intake I mean the upper tube the throttle body connects to.

Only thing I can come up with is that it richened up the mixture to compensate for the cool fresh air leak and has not tweaked back all the way. It gets a little better with each tank but it's still really bad mileage vs what I was getting. I don't see any run issues indicating it is now running real rich though. It's wierd.

 

[Duster]

This did eventually get better after a reset and couple tanks of fuel.

I replaced my PCM recently which reminded me of this because I noticed after the change it idles slightly worse but runs out better and also shifts a little different. Didn't really notice before. Slow decline I guess? Anyways, mileage improved a little more after PCM replacement. Back to what it was when it was pretty new.

So anyone having mileage issues should check the crankcase breather filter, PCV valve and PCV hose and elbows. If still bad and/or it seems to hold a high gear longer than you want and/or spark knocks, consider replacing the PCM.