I need some help with my 2000 Maxima SE. While under the hood chasing a coolant leak, I happened to notice a hissing sound with the engine running. Knowing that this typically means something is not correct with the air intake stuff, I started looking around and finally found the source. I have attached an image to help explain. The tube marked in red is not connected to anything (at the end where the red and blue lines are parallel) and is causing the hissing from suction being generated. If I place my finger over the end, the suction easily holds the tube to my finger so it is pulling a lot of air through it.

Question 1: is it supposed to just be loose and not connected to anything?

If no, then what is it supposed to connect to?

As for the other colors... From what I can see from the tube angles and lengths, I would assume that the red tube is supposed to connect to where the blue tube is currently connected. The red tube looks like it is designed to bend right to that spot. The other end of the red tube is the end marked with the arrow where a T junction connects it to that line near the top of the pic.

The blue tube looks like it should go somewhere else. If you follow the blue tube from the point where it is next to the red tube end, then it spirals back up and around and then back under some hoses, and then right back up to a T junction with the Green line where the T junction itself is underneath the point in the pic where the green and blue lines roughly intersect. So my reasoning is why in the world would the blue line spiral around through roughly 12", only to come right back to roughly the same spot to intersect with the green line about 2" from where it started. It also looks, from the bends in the blue line, like it should go somewhere else instead of that point where the red line ends without any connection. In other words, it is way too long and has way too much slack in it for where it is currently going.

Now, when I plugged the vacuum (end of the red line) with my finger, I could hear the idle speed changing. I've also had some issues with the car idling rough and even stalling out when cold - all things that are consistent with a vacuum leak after the MAF. This also makes me think that someone put these lines back together wrong.

Can someone please help me make sense of this? I realize this car is 17 years old, but she still runs pretty well for the most part and I want to keep her going as long as possible.

 

looks broken. one of those should plug in beside where the green one is but it looks like the nipple it connects to is gone

 

I was wondering that as well. The very few images I can find online that still exist show a second connection in that box where the green line is. However, I can't find a high enough resolution picture to compare to see where the hoses actually go. What I can tell is that the second hole in that box then connects to the same green line through a T junction, but there is also no sign of that T junction on that green line immediately in front of that box.

I assumed that mine didn't have that second connection for some reason. From the dirt in the hole, it's clearly been missing for a long time, if there ever was one.

 

Maybe someone reading this that has a 2000-2003 SE can take some pics of this area under their hood so I can compare?

Specifically, around the hoses I have marked in Red and Blue.

Please?!?!?

 

OK, I think I figured it out. After reviewing the FSM a few times, it looks like the blue line was indeed in the wrong place. The red line was supposed to connect to that point (Fuel Pressure Regulator). The blue line was supposed to go to the boost sensor attached at the front of the car hanging off the air intake (listed as Absolute Pressure Sensor in the FSM). The boost sensor has had nothing connected to it for years.

I've always wondered why there was a sensor hanging off the air intake connected to the electrical lines but nothing else. It seems this vacuum line issue may have been caused a few years back. I'm not sure why I never noticed the hissing/sucking sound until yesterday though.

I moved the blue line to the Boost sensor and connected the red line back to the Fuel pressure regulator. That takes care of the open-ended hose and corresponding vacuum leak. I'll test drive it shortly on some errands. Hopefully this takes care of the stuttery idle speed and occasional stalling when cold.

But this is going to drive me nuts wondering about who did this. Was it when we had the transmission replaced three years ago? Was it when we took it to another shop on any one of multiple occasions for other work, one of those times being an error code for a vacuum leak? In that case, they replaced the "accordion" tube right after the MAF. Maybe they screwed up these other lines while diagnosing that? Argh.... I wish I knew.

 

was going to take this for you yesterday but heres a pic of mine if you need it still

 

seems most likely for that to get screwed up if ever had to take the uim off for any reason (valve cover gaskets? maybe rear spark plugs?). could have been damaged while being handled or could be easy to plug things back up incorrectly. imo you'd have to be pretty careless to break that if you were only working on the intake area

 

Yeah, I agree. However nothing was broken. It was just clearly put back together wrong.

 

Cornholio has a Cali spec car. The Fed spec cars are different and that is what the op has. Here are pics of my fed spec 2k Max: