Going Bonkers Trying to Locate Fault. Please Help.

[ravashanks]

Hi all,

Would really appreciate some help. So i've been getting intermittent secondary air injection fault codes. Had narrowed it down to an improperly connected hose at the secondary air pump and thought it was solved, but fault code still comes up intermittently, though not as frequently.

On cold starts (though I can't really classify starting in the mornings in tropical Singapore a cold start per se) I get a very loud "Pff Pff Pff Pff Pff Pff" sound coming from the general vicinity of the secondary air pump (definitely from somewhere below the airbox). This sound disappears about 20-30 secs into the start up while the engine continues the warm up (i.e. sounds stops, no noticeable drop in engine revolutions). At this point, I was inclined to point at the secondary air pump itself as the culprit.

However, I get the same "Pff Pff Pff Pff Pff Pff" sound when driving under load (e.g. accelerating in 5th of 6th, going up a steep incline in 3rd or 4th etc...). Correct me if I'm wrong but the secondary air pump is only active during starts right? it does not come into play when the car is already in motion, yes?

Can anyone help me locate the source of this annoying sound? It does not alter the driving behaviour of the car. Engine still pulls strongly, cleanly and smoothly all the way to redline even with the sound. Of course if it could be pulling even stronger without the sound, i wouldnt know.

Some help much appreciated!!
(Ambient temps here in Singapore range from 25-28 deg Celsius in the mornings and evenings, never lower, and about 35-38 deg Celsius in the day)

[RS6BRIT]

Have you looked at the vac line that runs from the tee piece under the front carbon cover down to the power flap at the bottom of the air box ? If it's split or broken it could possibly make that sort of sound as it suck in air?

Easiest way to check by far is to pull it off at the tee piece end and then put a small piece of tube back onto the tee with a tight fitting screw in the end of it. Then start up from cold in the normal way and keep your ears open. It will at least eliminate one thing.

[ravashanks]

No havent tried that yet. Will be taking it to the mech's next weekend (and living through another week of the noise!) so will be sure to check that out. If that vac line is not working properly, would it not cause the entire vac system to malfunction? everything else seems to be working fine (exhaust valves etc...)

[RS6BRIT]

Vac leaks can be quite puzzling. Yes it should effect other things, but not always depending on the size of the leak. If its a pin prick then it might be small enough for the vacuum system to operate with parameters but still give you the odd noise. Likewise if its a small split, then it may only open as the engine angle tilts due to load, so maybe at idle and at certain loads whilst driving. Its worth a look, as its quick and easy to check.

[ravashanks]

Finally managed to find some time to bring the car round to the mechs to let them have a proper look. Turns out that certain parts of the exhaust (between cat back and headers maybe?) were not fully tightened so exhaust gases were leaking through that gap causing the sound i mentioned earlier. So that's properly fixed now and no more leaky exhaust sounds!

But now that the sound is gone, i realize that i'm getting engine knocking under hard acceleration... #facepalm