I have had a missfire problem and a 02 sensor error on both banks. I have already replace the air flow sensor and both up stream sensors. But the problem is getting worse by the day, car starts and ticks over perfectly.

I have just noticed when reving im getting a loud hissing noise from somewhere, so my question is this.
Does this sound like a vacume leak?
Could this be the whole problem?
and where is this leak likely to be ( sound like it's from the large pine between the air box and the engine intake just where the pipe bends, but i cannot see any holes in this pipe nor can i feel any air around it.

Many thanks

 

Only because I do not know anything but the hissing sound could be from a cracked bellows. Have you pulled the wole snorkel off to check for cracks on the underneath side. Simple to do and this way if not the issue you can eliminate this from discussion. But if it is cracked here are fix ideas.

https://www.jaguarforums.com/forum/s...ad.php?t=23576

 

Get a can of WD-40. Warm the engne to operating temp. Let it idle and spray around the bellows, at connection points and anywhere you think there might be a leak. If you find a spot where spraying causes a surge in the idle you've found your leak.

Even a loose clamp or a misaligned seal will do cause problems.

Good luck.

 

Thanks Scott, i will try this tonight