air intake hose

neathy said:

I have a 2003 gt 4.6l sohc and I'm trying to identify a hose that comes off of the air intake tube and goes to a metal tube on the throttle body that is below and to the right of The IAC and next to the ERG valve. Does anyone know the name and purpose of this hose ? With the metal tube on the TB blocked my car runs/idles fine but when I connect this hose the car either dies or goes to a very high (3000) idle. Thanks in advance for any info. neathy

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Are you sure the hose in question goes to the air intake duct? Or does it go under the duct to the PCV valve on the passenger-side rocker cover? IIRC (and mine's not stock so this is from memory...) there are two tubes coming out of the duct: The first goes to the silencer (black plastic thing) then to the IAC. The second runs across the top of the engine to the driver's side valve cover.

The hose you're talking about sounds like the vacuum feed for the PCV valve. The symptoms you're describing suggest that the PCV valve is stuck open and is thus a big vacuum leak. Replace the valve.

Make sure you get the right one as there were a number of PCV valves used on these engines. The parts guy may need your VIN number or even your car's build-date to know which one you need.

neathy said:

No, the hose definitely goes from the air intake to the throttle body. There is another tube that goes from valve cover to valve cover that is the pcv valve/hose.

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Hmm. Unless I'm missing something, something on your car sounds incorrect.



In the above pic, you can see the long, stiff plastic tube that runs from the driver's side valve cover to the passenger side of the engine where's it capped by a red plug. You can also see the IAC "block" whose hose-end is resting near the filler cap. These two hoses are the ones that plug into the air inlet duct (absent in these pics.)

The hose you're talking about can be seen running from the throttle body, under the IAC hose, under the red-plastic vacuum manifold and over to the passenger side valve cover to the PCV valve.

Take a pic of your set up and post it. It doesn't sound right.

neathy said:

please see previous post with picture included. Thanks, neathy.

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I know which hose you're talking about. You said "No, the hose definitely goes from the air intake to the throttle body." and I'm saying this is not correct. This is just bypassing the throttle body and IAC by connecting the hose from the air intake to the plenum.

See the picture I posted above. The plastic tube doesn't go valve-cover to valve cover. One end goes to the driver's valve cover, the other to the air intake tube (which isn't shown in that pic; the red plug shows it obviously doesn't connect to the pass-side valve cover.) The vacuum source for the PCV valve is the hose you're talking about: its hose runs from the PCV valve on the pass side valve cover to that port on the throttle body, to the left and below the IAC hose connection.

The PCV system operates like this: Fresh, filtered air is made available to the driver's side valve cover via that hard, plastic tube connected to the air intake. Under certain operating conditions, the vacuum applied to the PCV valve will open it, allowing the vacuum supplied from the TB to draw this fresh air and fumes and gases through the crankcase and into the intake manifold. You can't just connect both valve covers with a rubber or plastic tube. That's no ventilating anything.

Post another pic (or several) showing all the hose connections involved.

When did this happen? That is, did the car just start acting up or was something done to it (e.g. spark plug change, installation of a CAI etc) and after re-assembly, it's now wrong?

LOL. It happens to the best of us. In my car's case, the shop that installed the supercharger last winter did something even more egregious:

They connected the cross-engine breather hose as expected (i.e. from the air intake to the driver's side valve cover) but then proceeded to put a little breather filter on the PCV valve. PCV valves are vacuum operated: When there's a strong vacuum they close (e.g. idle) and are open at load (e.g. WOT). So when these guys did this, they built in a vacuum leak. Since the PCV valve was essentially open, the air intake duct was exposed to the air via the open PCV valve and filter. The car had issues idling after the blower install which I traced to this. After re-plumbing it properly, everything is much better now. Still...a vacuum leak of that size on a blower car...

Glad to hear yours will be fixed easily.