I've been getting a check engine light with a P1492 code (Downstream Throttle Air Leak) on my 2007 Mini Cooper S (R56 with N14 engine). I can clear the code but it comes back about a week later. There is a hissing sound coming from the left rear side (on the left when facing the engine, it's on the right side of the car from the driver's position) of the cylinder head cover after I shut the engine off. The hissing lasts for about 20 seconds and as it slows down, it "burps" and goes for another couple of seconds before stopping. The car is not running as well as it used to. I'm assuming this hissing sound is not "normal". I took the cylinder head cover off but could not see anything apparent but I really didn't know what I was looking for. The hissing seems to come from the back side of the cover next to a hose that connects on that back corner about in the center of the photo I've attached.
I wanted to check with the experts on the forum before I spring $300 for a new cylinder head cover - is there anything that can be done to fix the cover or is replacement my only option? Thanks for any advice.

 

What year is your MINI? This sounds like a vacuum leak and I bet it is that hose. I took mine off when I blocked the PCV and I put it back on when I wanted to use a boost gauge again and in the time that it had been off it developed a crack. I t was not surprising because it is crap thin plastic. So I took it off again and cut the plastic tubing off the connectors and went and bought fuel line hosing and reattached. No problems since.

 

It's a 2007 and it has about 60K on it. I had the timing chain replaced by the dealer after the "death rattle" and have finally gotten reimbursement for what they charged me. This vacuum problem did not appear until after I'd taken it in to the dealer so they could "check that the timing chain assembly had been replaced" after I was notified of the recall. I don't know if their work contributed to the leak or not.