Ben1112

Hello,

My 2003 Malibu LS 3.1L was running rough at idle. The code indicated a lean condition. Utilizing the fuel trims I concluded it was likely a vacuum leak.

i found one vacuum line that had a piece of broken rubber on it but can’t find where the other end connects. Wondering if it is supposed to be plugged. One diagram doesn’t show it but others indicate it as to accessories.

when I plug it the idle is perfect but the fuel trims at high rpm indicate a rich condition. Do these take awhile to normalize? Is this supposed to be capped? Thanks for any help.

Located right in front of alternator.

oilcanhenry

If its affecting your fuel trim it must plug into something. I cant see from the picture which hose you speak of. Can you elaborate?

Ben1112

It is the little metal coupling right in front of the alternator. It doesn’t have a hose on it, it just had a small piece of broken rubber on it.

mountainmanjoe

looks like the main vacuum source. Typically it goes to a checkvalve and spherical reservoir around the passenger wheel arch, before going through the firewall to the HVAC controls inside. Sometime there' a sticker with vacuuum routing diagram right under the hood.

Ben1112

There is a schematic or the lines on the strut tower but this port is not highlighted. That is why I’m wondering if it supposed to be capped. Other schematics for similar vehicles refer to it as “To Accesory”.

mountainmanjoe

Does your vent selector work?

Ben1112

Yes but it sounds like a puff of air is emitted when switching between them.

oilcanhenry

If it doesn't seem to go to anything, but it has vacuum then yes you'll need to cap it, as it will allow unfiltered air into your engine

Ben1112

Thanks for the help. I will cap it and see how it goes. It sounds much better capped and doesn’t chug (can feel it) but I’m concerned about the fuel trims indicating its running rich.

kevinkpk

mountainmanjoe
looks like the main vacuum source. Typically it goes to a checkvalve and spherical reservoir around the passenger wheel arch, before going through the firewall to the HVAC controls inside. Sometime there' a sticker with vacuuum routing diagram right under the hood.


It is. The op needs to trace the tubing back, and reinstall it. I can't believe it will even run.