This post as far as I know is only for the 97 vw passat wolfsburg edit, AAA engine, VR6 GLX Automatic Trans. Just a heads up on the replacement of the Kombi valve located snugly under the maniflold on the front of the vr6 engine. After alot of reasearch and suggestion on just how to get the Kombi valve off to replae the vacuum lines and put a new kombi valve back on , it has been suggested that you have toeverything from takeing off everything from the front bumper all the way down to removing the upper manifold just to get to the valve. Well, I'm here to tell you that you don't have to do ANY of that which other forums suggest. You do have to start with alot of patients because that is what will make this job a success or failure. If you use a swivel socket and an extension with a little of masking tape to stiffen the swivel up just perfectly and have small enough hands and a good light you can actually get to the one star headed bolt holding the kombi vale on. Once you get that bolt out, you give the valve a little twist and out she comes. Now, since you only want to do this job once, go order yourself some HI TEMP vacuum line from Napa. It runs about $11 for 6 feet of it but it is rated to withstand temps up to 400 degrees. While your into it, just go ahead and replace any fabric covered vacuum lines with the other 5 feet of the orange hi temp line because you will eventually have to replace it as well. The fact that kombi valve usually burns up is because of the rotted vac lines.
The function of the kombi valve is to keep the car in closed loop upon starting your car. once the car starts, the Secondary Air injection pump kicks in for about a minute or two allowing fresh air to be introduced into the exhaust that exits the engine. Once that combusted air mixes with frest air it helps to warm up the catlyic convertor quicker so the o2 sensor can get a quicker reading as to the amount of air and fuel to mix to get the engine up to proper and peak running performance. Once the computer gets the correct information, it can adjust the air fuel mixture to open the loop and run properly. Sooo, If your vacuum lines are dry rotted and not allowing a vacuum to be pulled on the kombi valve and shut it off, the valve stays open and the exhaust fumes from the intake reach into the kombi valve and burn up the fragile little rubber diaphram located in the Kombi valve. Since there is no way to shut off the kombi valve, your car stays in the Closed loop and causes it to run hotter and use more fuel. Sooo, if you have dry rotted vacuum lines and have had them for awhile, you have probably burnt up the diaphram in the kombi valve. Since the Kombi valve is injected with hot vapors from the intake and not able to shut off, this causes condisation in the valve that eventually drips down into the plastic coragated hose leading into the big black secondairy air injection pump. If you live in colder climates, this condisation will freeze and bust the Secondairy air injection pump. You don't want to have to replace the pump either because it runs about $350. If you are tripping the check engine light, first start with the vac lines, then the kombi valve and then the sap, then the solanoidj($55) then the relay mounted on the firewall and marked with code 111 ($15) at NAPA. The oem solanoid is made in the usa and is not that expensive. Any questions, just hit me up. I have been working on this P4011 code for about 2 months and have learened ALOT.