I'm trying to track down a suspected vacuum leak and upon eyeballing the various pipes, I came across this pipe which seemed a bit suspicious. It has a kind of sleeve around the section where it bends. I'm not sure if that is standard and also I have no idea if this particular tube is at all one of the various suspects in vacuum leaks. I'll try to attach a photo. The tube in question is the one at the bottom of the photo.

 

That particular tube is part of the supercharger system and has coolant in it.

The sleeved appearance is normal.

 

Why do you think you have a vac leak?
What's happening?

 

I got error codes showing P0171 and P0174. The long term trims were high at idle but came down a lot while driving on the highway. Actually the car goes well but the idle is about 100 rpm higher than usual. The MAF sensor seems good and there’s no misfire or rough idle so I guessed it was a small vacuum leak. I knew those hoses were from the supercharger but didn’t know what their purpose was. I guess the next step is a propane test.

 

Could be that the two VVT O-ring seals are leaking. Do you see oil seepage around them? My wife's 2006 XK8 is on its third or fourth set of these seals. They bake in the engine bay heat, get hard and brittle, then tend to leak. I have seen P0171 / P0174 codes as a result....

 

Look into doing a smoke test instead. There are so many places an air leak can come from. Remember, these codes pop up when the total air leaks push the ECU to add 25% more fuel than what the air flow meter measures. There can be more than one air leak...

 

Cracks in the concertina air intake pipe are always suspect. Underneath where you can't see them.

 

Jon, I can't see any kind of oil leak. Everything looks clean. My Jag mechanic replaced the bank 1 upstream sensor a couple of months ago and he did a quick check of the engine but he didn't find any leaks.

 

I thought I'd do a propane test first as it's pretty easy to do myself. If I find nothing, then I'll have to hunt around for a smoke test.

 

Mike, I'll check that out. Thanks for the tip.