'04 Cayenne V6 Intermittent Intake Leak Noise

[Nana's_914]

My '04 Cayenne V6 has 65K miles. The Check Engine Light has not come on.

When I start the car cold it has a slight missfire that goes away when warm. When warm after start it idles normally for about a minute then there is a noise that sounds like an intake leak. If I rev the engine the noise goes away and slowely comes back. Here is a video...the noise start up at about 50 seconds in.

Any idea what this could be?

I recently changed the primary fuel pump and fuel filter. I am concerned that the low fuel pressure from the failing fuel pump caused this issue with a missfire or detonation.

[Nana's_914]

I am a bit baffled by what is causing that noise. Is it something normal like the secondary air pump? While poking around I noticed that the PCV is drawing air in through the top cover. When i cover the square vent hole on it it sucks on the tip of my finger and makes a whistling sound. I assume that is not normal and have ordered a new one.

[Loren]

Have you cheeked for pending fault codes (since it seems to correct itself)?

[Nana's_914]

No, I can check tomorrow.

[wvicary]

Sorry my hearing is rubbish and I couldn't identify what noise you're referring to. There is a small bleed hole on the PCV to equalize pressure on one side of the diaphragm and it shouldn't be drawing a vacuum so you're correct to replace that unit. I would also check for fault codes and clean the throttle body.

[Nana's_914]

No CEL or pending codes.

Can leaking PCV effect variable cam function?

Addition info:

There is a light gas smell in the cabin on cold startup.

It is about time to change the oil the 2000mi service light came on. The level is spot on and I have not had to top off.

Edited January 24, 2012 by Nana's_914

[Nana's_914]

I can try cleaning the TB. Doesn't sound like a bad thing to do at all. Should I clean the MAF while I'm in there?

[Loren]

MAF has little to do with idle - I would leave it alone.

What tool did you check for pending codes with? I doubt anything but Durametric or a Porsche tester (PST2 or PIWIS) will show all pending codes.

[Nana's_914]

I have given the tester back to my friend, and don't remember the model, I can find out later. It was not a Durametric or Porsche tester. After trying to read the codes I tried to do a pending code transfer per a mechanic friend's suggestion. Procedure was supposed to transfer pending codes to CEL. Not sure I did it right, because I got no codes. What I was told is run the car for a few minutes then turn it off and toggle the key multiple times. Does this procedure sound like something you have heard of?

[Nana's_914]

Tester was an Actron cp9180.

[Loren]

See if you can get a hold of a Durametric, Porsche PST2 or PIWIS tester - thye all support Porsche's advanced diagnostics.

[Nana's_914]

PCV swapped out and oil changed. No change in random noise. Poked around some more and discovered the intake leak noise stops when I pinch the line on the left side that goes to, I believe, the purge valve.

Is this normal for the purge valve to function like this? If not, where is the purge valve and how do I change it?

Got access to a proper tester this morning. Pending code present was P0335 - Crank position sensor.

Code was reset and did not come back yet. Would an oil change effect this fault? I am tempted to just change the sensor out as PM. Any tricks to changing this?

[Nana's_914]

Sorry my hearing is rubbish and I couldn't identify what noise you're referring to. There is a small bleed hole on the PCV to equalize pressure on one side of the diaphragm and it shouldn't be drawing a vacuum so you're correct to replace that unit. I would also check for fault codes and clean the throttle body.

I am new to the Cayenne and it is not obvious to me how to get the breater line off the intake elbow to gain access to the TB for cleaning. It looks like it needs to be pinched to release, but I don't want to guess and break it.