EGR valve maintenance

[RudyH]

So curious if anyone had performed any maintenance on them before?
https://www.ecstuning.com/Audi-B8_S4...ne/Emissions/2

Issue is I got p0491 / p0492 codes that popped up. I know before you say 'carbon build up'...there are some interesting symptoms...
So the code came up last winter, and I cleared them. It got warm, and the code never came back. Sweet, false alarm...this winter comes and suddenly drops below 0 and the code comes back. It warmed up on the weekend and the code disappeared...where Monday morning it dropped and the code came back.

Took it to the mechanic, and he agreed, doesn't sound like carbon build-up or it would have stayed on due to restrictions.

It turns out he said the EGR valves or combi valves are stuck and not opening wide enough so he wanted to replace them. The first thing not covered by my aftermarket warranty go figure...the pump does seem to be running fine though.

Any ideas? Unfortunately, not a whole of them floating around the wreckers, and it sounds like due to labor you might as well just put new ones in

[schirm]

So curious if anyone had performed any maintenance on them before?
https://www.ecstuning.com/Audi-B8_S4...ne/Emissions/2

Issue is I got p0491 / p0492 codes that popped up. I know before you say 'carbon build up'...there are some interesting symptoms...
So the code came up last winter, and I cleared them. It got warm, and the code never came back. Sweet, false alarm...this winter comes and suddenly drops below 0 and the code comes back. It warmed up on the weekend and the code disappeared...where Monday morning it dropped and the code came back.

Took it to the mechanic, and he agreed, doesn't sound like carbon build-up or it would have stayed on due to restrictions.

It turns out he said the EGR valves or combi valves are stuck and not opening wide enough so he wanted to replace them. The first thing not covered by my aftermarket warranty go figure...the pump does seem to be running fine though.

Any ideas? Unfortunately, not a whole of them floating around the wreckers, and it sounds like due to labor you might as well just put new ones in

These cars can be funky in the cold. My ADS module would randomly stop working last winter on the really cold days. But Once I cleaned my garage and park in there it has never happened again.

[RudyH]

Just adding this ... been using One Note too much ... for reference for everyone when they need to start troubleshooting and need cheapest pricing

https://www.carpartsdiscount.com/cat...html?3594=2184

[chaos2984]

Umm last time I checked the engine doesn't have EGR anymore. Its all done with adjustable valve timing now. Those are your SAI (secondary air injection valves) Entirely different than EGR. All the SAI is for is to help bring the converters up to temp faster.

A flow problem since your getting it on both banks, My guess is from most likely to least likely, The pump is having issues or the valves are not opening correctly. Its a flow problem. So like your mechanic said your valves could be sticking and not opening correctly or your pump is weak when its cold out. Those systems sux to diag when you have flow codes.

[RudyH]

Umm last time I checked the engine doesn't have EGR anymore. Its all done with adjustable valve timing now. Those are your SAI (secondary air injection valves) Entirely different than EGR. All the SAI is for is to help bring the converters up to temp faster.

A flow problem since your getting it on both banks, My guess is from most likely to least likely, The pump is having issues or the valves are not opening correctly. Its a flow problem. So like your mechanic said your valves could be sticking and not opening correctly or your pump is weak when its cold out. Those systems sux to diag when you have flow codes.

I think it's the same valve we are both referring to...EGR valve or combi valve - they are listed parts for our cars

The mechanic said he can see flow, but can't tell how much since the valves aren't opening up all the way so he said he would try that first before going after the pump

I thought *maybe* you could throw something at it to make the sticky valves work again, but sounds like with all the work involved it's easier to replace. $200 parts but a lot of work to get to them

Getting also an O2 sensor fault, which I forgot to confirm this morning but was in historical so I didn't notice it before. Seems generally these are tied together.