# Engine trouble



## craig0423 (Mar 2, 2010)

I have an 99 A6 Quattro, and im having a little trouble with the engine when it gets warmed up i seem to lose hp in the upper RPM range It gets worse the warmer the engine gets but when its cold it works fine. I have a check engine light on but I was told that it was just a lose connector that I need to replace and I dont think it has anything to do with. If anyone can help it would!!! Thanks


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## tryin2vw (Dec 30, 2006)

Post the actual codes you received as a starting point, please. It will help tremendously.


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## craig0423 (Mar 2, 2010)

Ive got to re run my codes ill do it monday and re post them then, I do most of my own work. I took it to a vw/audi specialist that im good friends with, hes the one that told me it was just a wire that was lose... but that was before i started having this problem.


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## craig0423 (Mar 2, 2010)

P0411 secondary air injection system incorrect flow 
It says probable cause is faulty air combination valve 



craig0423 said:


> I have an 99 A6 Quattro, and im having a little trouble with the engine when it gets warmed up i seem to lose hp in the upper RPM range It gets worse the warmer the engine gets but when its cold it works fine. I have a check engine light on but I was told that it was just a lose connector that I need to replace and I dont think it has anything to do with. If anyone can help it would!!! Thanks


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## tryin2vw (Dec 30, 2006)

There are several potential causes of this. 
Check that the electrical connector for the solenoid on the intake manifold is operating. It will only operate for the first 90-120 seconds after the car has started from cold, so check it first thing in the AM on first start-up of the car. Let the ECU open it while you test for a down stream vacuum. If you use the battery, it may test ok that way but still be bad because the ECU puts out less power than the battery directly. 

Check the vacuum lines. There are several that can leak, causing issues. It takes about 10 feet of 3.5mm high temperature silicone vacuum hose and an hour to replace them all with new to eliminate that potential leak point. Do them one at a time to not get them crossed. 

Check that the combination valves work. They are located on the back of the heads and look like silver mushrooms. 

Sounds like a vacuum leak to me.


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## craig0423 (Mar 2, 2010)

Is there a diagram I can get other than the manual?


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## tryin2vw (Dec 30, 2006)

There is a vacuum diagram on the hood or on top of the lock carrier. It will look like this:


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## craig0423 (Mar 2, 2010)

yea so I did some work on it and I think the Secondary air pump isnt working... can anyone tell me how this thing is suposed to work... cause you would think being an air pump air would be flowing through it but its not. I dont know if its suposed to be constantly flowing or just pump some of the time?? can anyone help?


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## O_o (Nov 12, 2009)

It should only be on for a few seconds after a cold start.


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## tryin2vw (Dec 30, 2006)

*SAIP system*

From a cold start, the SAI pump should run for approximately 90-120 seconds. In no particular order:

Check the vacuum lines to the Combi-valves.

Check the solenoid above the intake that provides the vacuum for operating the Combi-Valves.

Check the fuse for the SAIP. It is in the box with the ECU.

Check the relay for the SAIP. It too is in the ECU box.

If the fuse is good, try jumping the relay base to make sure the pump runs.

Make sure the Combi-valve operates by providing vacuum to them and verifying they open, one at a time.

Make sure the hoses to and from the SAIP are connected properly.

Verify the integrity of the metal hoses on the engine, including the flex joints at the Combi-valves.


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## 2001 Variant (May 27, 2007)

The secondary air system is only active during the first minute or so after a cold start (as mentioned by others already). It's only purpose is to inject air into the exhaust during a cold start so that the catalytic converter has enough oxygen to burn the unburned hydrocarbons present in the exhaust gas (due to the engine running rich before closed loop control starts). This also helps heat up the cat which cuts down time before the cat can work at full efficiency. There is no performance (or fuel economy or long term damage) penalty when this system is not working besides the annoying Emissions Workshop message and MIL and of course increased emissions during the first minute or so after a cold start. If you don't have to get emissions tests done where you live you can easily ignore SAI problems.

Since you say that you have performance issues this points away from the SAI as the root cause because there should not be any impact. It sounds more likely that the SAI issue is the symptom of another problem along with the degraded vehicle performance. As others have suggested it is very likely that you have a vacuum leak. The valves through which the SAI injects air into the exhaust manifold are vacuum operated. If you have a leak they will not open properly and you will get reduced flow. The leak most likely would also impact other areas (for example the intake changeover valve which is also vacuum operated or simply ingress of unmetered air in the intake) which would explain your performance complaints. On the other hand this would most likely impact both banks of the engine so you should see two SAI insufficient flow codes (one for each bank).
Another possibility is a bad oxygen sensor. If the sensor is not bad enough to throw a code of its own it could still be bad enough to hamper performance and could be responsible for the SAI code since the flow in the SAI system is diagnosed through the pre-cat oxygen sensors.
Another option could be that the two issues (SAI code and bad engine performance) are not related and are just coincidental.
If your air pump was bad you should get a code for each bank since both sides of the engine are equipped with an SAI valve and both are fed from the same air pump (and controlled through the same vacuum solenoid and supply).


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