So I went to replace air filter and I noticed one of the vacuum hoses appeared to be cracked with a hole at the top. I didn't have any replacement hose available so I cut the cracked end off and stretched it out to fit. Ever since then the car has been throwing a p0411 code and I'm assuming that is what is causing it but had a few simple questions about it and was hoping for some help.

First, does what I described sound like what would be throwing the code or could it just be a coincidence? The vacuum hose I replaced is the one circled here and the car is a 01 A4 1.8T:


Second, if that is the problem, does anyone know off the top of their head what size that particular hose is? I was planning on ordering it from ECSTuning so that I would have extra in case another one needs replaced and didn’t know whether to get the 3, 4, 5, or 6 mm size.

Thanks in advance for any help.

 

Definitely possible that this is the cause. P0411 is secondary air injection incorrect flow or some such. I ordered 15 feet of 3.5x2 vac line from ECS and replaced every one i could find. Thats the size you'll want for the line you circled. FWIW, the 1.8T has a bunch of larger boost/vac lines that also tend to leak over time, those will need to be ordered and replaced individually

 

Awesome, thanks a lot. Just ordered 3 feet of it and should have it in time to take care of it over the weekend.

Thanks again for the help and I'll keep the larger boost/vac lines in mind for the future.

 

no worries man, glad to help. As long as we're on the topic, all of those larger hoses can be found here. I can't think of a reason you'd need to replace the hard lines but the rubber S's and elbows and all that other weird **** are all there.

 

Thanks again for all the help. I got the lines replaced and everything seemed good for about 50 or so miles but then the CEL came back on. At that point a burning rubber smell started to occur as well.

I've checked the lines thinking that they might be touching a part of the engine and heating up but they appear to be fine and have enough slack in them to avoid resting on the engine.

Any ideas?

 

One of your hard hoses from the SAI pump most likely broke.

Ok now that im done with lunch ....

The SAI system can be faulted by a faulty vacuum hose at the combi falve on the back of the head, the pump failing, or hoses being broken. Simple to check are the small hose to the left of the intake pipe coming out of the airbox, the vac hose coming out of the metal cylinder out of the back of the head, and the SAI pump operation. On a cold start, get down in front of your pass tire and listen for a mini vacuum sound, if you hear it faintly then good. If its LOUD then the pump failed ($300) Above the turbo, there are 2 hard metal pipes, one goes into the intake boot, and the other dissappears under the intake. You of course need to track the harder one. Either pull the belly pan and look from under, or remove the intake boot (about an hour depending on your luck with single use hose clamps) That metal pipe should go into a ghetto plastic hose ($56), that usually cracks or breaks then into the air pump.

 

get it up to temp and look under the hood...

 

This is where the hard hose connects to the plastic hose, mine broke at the L section.
You will see this after removing the upper airbox and intake boot. You can see my cute little K03 and headlight


How I patched it:

 

Just got home from work and popped the hood. There was some smoke coming from the other side of the engine - away from where I replaced the line. You'll have to forgive my lack of auto knowledge so I included a picture to show where the smoke seemed to be coming from.



The smoke was just white/gray, there wasn't a ton, and it stopped after about 5-10 seconds. I also couldn't tell if it was coming from the engine itself or below in that metal pan thing.

 

The metal pan thing is a heat shield. The thing that sorta looks like a grenade with the wire coming out of it is your catalytic converter, the wire is for an O2 sensor. The metal thing forward of that is your turbo

Smoke coming from that area could be a bad valve cover gasket leaking oil onto your exhaust mani. Take the plastic engine cover off and you'll be able to see better.