Originally Posted by mardimus

Its has been a few weeks and I have done some extensive research trying to sort this out. Modifying would be an option but a pain trying to find someone to code out the ECU to get ride of the SAI. I am only getting one code (listed below) not two, I had a wire unhooked. So here is where I am at....

I replaced all vacuum lines with new ones. I replaced both solenoid valves. I removed and cleaned the driver side combi valve. I have a vag com with VCDS and have used the output test to test both n112 valves (solenoid) and they appear to be working. I also hooked up a hand pump to each Combi valve and they hold vacuum and can also hear them working. When I use the Vag to run an output test on the SAI pump, it runs and slows, runs and slows. But when the car is on it seems to run on full. I have removed both hoses to the pump and can feel suction and air coming out. It appears the pump is fine.

Given that I am only getting one code, P1423 (17831 vag), is it possible the pump is running low? or not enough pressure in air coming out? You would then imagine I would get two codes.

It did take a while to clean out the driver side combi valve and I would have tackled the passenger side as I think it could be the culprit but it is a pain in the *** to get to.

I have not checked the relay and fuse in the ECU but only because my theory remains that if it were the pump, would I then throw two codes and not one?

I am stumped here and I can only wrap my head around cleaning the passenger side combi valve next. I just do not know how to get to it without removing the engine head or the engine itself. It is tight.

Any thoughts would be greatly appreciated. And thanks to veedub420, and b5blazing for the thoughts and confirmations of a few things, it is much appreciated. Cheers.

Here is a pic of the areas in question:

I also found this writeup and it has helped a bit. I did not clean out the exhaust port on the driver side as it seemed semi clean and not thick. I was afraid of creating blockage and a potential problem. But here is the writeup:

""""Secondary air injection seems to be something sooner or later every Audi owner has a problem with. Let me run down the symptoms and then the steps to fix them. This should be the definitive guide on how to repair the system. If you had an issue & repair that wasn't covered by this guide, please shoot me an email.

The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.

The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.

Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.

Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.

The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.

So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup."""

Originally Posted by tommyleea

I ordered a new SAI hose that goes to the air cleaner box. I will pick it up this weekend, and see if that eliminates the codes. I noticed that the other SAI hose, that runs up to the pipe, is not on very straight. How exactly does that hose connect to the pipe. Does that plastic ring somehow hold it on the pipe? Also, I noticed that there is a bracket with a nut that is connected to the metal pipe. I see where it should bolt to, but mine is bent up towards the pipe. Is there a reason, maintenance wise as to why this would be. I guess I will try and realign it with the bolt hole. Thanks for advice.

TommyJ 00 A4 Q 2.8