charlieaf92

I've noticed that when I hear a bit of a whine from my engine compartment when at a stoplight (I'm assuming this is the secondary air pump running) that the engine sounds really awesome when I blip the throttle. I'm assuming this is related to additional airways being opened up to the intake while the pump is on. I'm just curious if anyone else has noticed this, and if there has been any thought/discussion about ways to modify the intake to give this effect all the time, or at least at idle speeds?

Cheers
Charlie

808Bill

Charlie, mine would kick back on when come to a stop five minutes after driving...Now after 6 months my AOS failed. You should check yours(AOS) with a manometer and confirm your AOS is functioning properly before it fails.

charlieaf92

Thanks for the tip! I'll start paying more attention to how often it comes on. It is pretty infrequent, but I don't pay that much attention. I'll also look into getting a manometer. When I did my IMS Solution I did the poor man version of the check (removing the oil filler cap with engine running to ensure it didn't stall out).

DBJoe996

The secondary air injection system pumps air into the exhaust headers and really has nothing to do with the air intake system. It is doing that to fool the O2 sensors at cold start, and they report back to the DME that all is well. Maybe your "blipping" is opening the intake resonator.

jumpy chunky

DBJoe,
Thanks for the explanation of resonance flap.
I'm not sure what the numbers stand for after the M96 designation though. Are they model years?
If so the what do the numbers stand for in the second paragraph? Probably dumb question,
but I have a fault code P1516 on my car. So am wondering what I'm missing out on. MY '99'.
TIA.

cds72911

M96/01, M96/02, M96/03 et al. were all different subsequent generations on the M96 engine.

DBJoe996

Ahsai

Please see this thread for more info on p1516
https://www.renntech.org/topic/29087-fault-code-p1516/

Dan951Man

It sounds different because, besides running rich to supply additional fuel molecules in the exhaust, the car is also retarding the ignition timing to get more heat into the Cats. The air pump delivers the extra oxygen molecules and you get extra heat in the cats to light them off and go into closed loop as fast as possible.

You know what also retards the timing? The clutch switch (the cruise control switch at the top of the travel, not the starter cutout switch at the bottom of the travel).
pay attention to your exhaust tone and press the clutch pedal in and out for similar effects

jumpy chunky

Okay, I see those are engine code numbers.
Thanks everyone for your replies. I will have to do some digging to locate change over valve and wiring. Will post if I find the culprit.