Engine management light / Exhaust rattle

[wellzieRS4]

I have had engine management light come on a couple of times the code is
0491 secondary air injections system bank 1 and i have noticed that the exhaust rattles at the end pipe on start up for a minute or so.
Anyone know what this could be and if the two are related

[Steve_C]

My exhaust also rattles when cold - not sure why. I don't have a engine mgt light on though....

[silverRS4]

The secondary air injection flow (during the catalyst heating phase on start up) is controlled by a solenoid and requires vacuum. The solenoid is under the manifold, in the engine "V" and uses the same vacuum source as the manifold flaps, power flap and exhaust flaps. I'd say you have a vacuum leak. As far as I know, the catalyst heating period, when the secondary air injection pump draws fresh air from the air box and pumps it into the exhaust ports on the cylinder heads, is the only time the secondary air system is activated.

[ArthurPE]

beat me to it, lol

you probably also have some loss of performance, possibly intermittent...

[wellzieRS4]

Thanks for that, my engine has been out recently to fix oil leak may a pipe has split or not back on properly i havnt noticed any loss in performance it pulls like a train

[wellzieRS4]

so far I have had the secondary air pump replaced and they said they found a kinked pipe under the rear bumper and repaired that, they said they have also replaced a solenoid all at a cost of over £1000 got the car back yesterday started it up this morning and the flap are still rattling i think I'm being ripped off, the top tech came out from Audi to see the problem from cold start up and he said i needed new flaps til i showed him this post don't know what else to do, anyone got any ideas?

[P_G]

Mine also rattles on cold start up albeit for 10 seconds or so. I suspect that all will to a certain extent as I believe although am not sure that the engine does not have the capacity to hold vacuum pressure so will need the initial seconds to establish vacuum pressure again.

Easy way to check is when you hear the rattle in your exhausts feather the throttle to 1-1.5k rpm for 5 or so seconds and then let it idle. It should go after that, if still audible you have a problem.

[Steve_C]

my rattle (and slight loss of power) was fixed by audi by replacing a solenoid.