I recently purchased a 2000 Audi A6 4.2, realizing that it may need some work. I knew that it need a linkage arm between the changeover valve and the actuator control arm (driver's side, which I believe is bank 2).

I realized today that the changeover valve for the unbroken side isn't working properly either. With the engine off, at idle, or at RPMs >4500, the passenger side changeover valve is deflated.

That made me realize that the actuator arms are seized. I can't move them by hand at all. I've read in many forums today that a seized actuator isn't necessarily uncommon, and that it can even be fixed without removal of the intake manifold, etc. (which I need to do anyway eventually because of a faulty knock sensor).

What I find really odd is that the actuator arms are seized open, or actuated - actually against the force of the spring. I can't imagine how this could happen outside of a mechanical bind vs. simply corrosion, buildup, etc.

So, my question is this: While I am prepared to dismantle the intake manifold if I can't unseize them the non-invasive way, is the fact that they are seized while actuated a sign of a huge internal problem with the butterfly valves, etc.? I called my local independent Audi mechanic and he simply left it as "that's bad." I realize that - but how bad? Or, is it not uncommon when the arms seize to actually seize while open?

 

Are those valves controlled by vacuum lines and have you tried actuating the valves and solenoids other than by hand.

As far as the knock sensor goes. Just wondering what is happening that makes you think it's bad. Audi's are so prone to misfires and those sensors are fairly simple.

Better question. Is this your first Audi? and have you performed any work on it yet? If your just starting out we can walk you through service items that you need to do that may resolve a lot of the issues your having.

 

Thank you for the reply - yes, this is my first Audi. I haven't done any service on it myself (yet). Since the car doesn't seem to be in any immediate danger from the problems (from what I've read, at least), I'm taking my time and just reading and researching a lot before I do anything I'm not comfortable with.

There are a few codes being thrown with the CEL - Knock Sensor [I believe Bank 2], Low Input. I've read that can simply be a torquing issue but that it's such a pain getting to them that I'm better off just replacing them since the car has about 96,000 ticks on it so far. I'm also getting a "Running Lean" code.

The valves are controlled by vacuum lines, which I can clearly see are disconnected on the driver's side (again, I think that's Bank 2? I don't have my Haines manual yet). With the engine running when I tug on the passenger side valve I can tell it is getting suction. It's my understanding that when the valves open/close, the linkage arms that are connected to the intake manifold actuators should move the actuators - as opposed to the actuators opening and closing the valves. I haven't tried moving them other than by hand, but according to the Audi materials I've read, both valves should be inflated, with the actuator arms at rest with the power of the spring pushing them "down" or "in" when the engine is off. Whether the engine is on or off, both of the arms connected to the intake manifold are in the actuated position, stuck against the power of the spring.

I think this answers your questions. I can see the arms getting seized, but it seems extremely odd to me that they are stuck in the position they're in.

 

I haven't had that problem with mine but I do have a 2000 4.2 in my A8 so I'll check them.

These cars are prone to electrical problems due to faulty/dirty connections. As far as the Knock sensor and every connector you come across as you service these cars. Pull the terminals apart clean them with a nail file or brush apply di-electric grease and re-assemble. It makes a world of difference. The ECM sends variable voltage through the wires so any additional resistance will send the ECM false info.

Don't get me wrong that sensor could be bad, It's just more likely to be a bad connection or damaged wire.

You should also replace all of your vacuum lines. You can order OEM braided lines at www.ecstuning.com it's cheap. Then it's done. Otherwise they will break every time you go in there to fix something.

The manual you seek is not a Haines. You need a BENTLEY! Go to bentleypublishers.com you can download it or order the cd. You can also get one from Blauparts.com

To pull the codes you need either a VAG-COM from Ross-tech ($200) or you can read through the forum some guys have the $20 ebay scanner working somehow. A generic scanner like my Actron will not pull all of the AUDI codes so what good is that.

Do you know when the Timing belt/ waterpump/ thermostat etc...etc... was last replaced?

You will need to replace it at 90K intervals. Just did mine for the second time. Audi did it, Belt only the first time- What Slackers.
The 4.2 is prone to thermostat failure. Guess where it's located! Under everything. I believe all of the parts and timing bar/cam adjuster tool cost me about $800.

Also you will need to have someone service or at least top -off the transmission fluid. The trany is a 5K rebuild so make sure it's full with no leaks. If your mechanically inclined I can explain the process otherwise find an Independant Audi/BMW dealer familiar with these transmissions. NOT Jiffy lube or some wanabe shop. They don't fill like American cars they fill from underneath, what a PITA.

 

Thank you for the great advice - I'll check the connections. Since you have the same engine, let me ask you - is it a powerful machine to drive when it's functioning? Frankly mine is a bit underwhelming, especially from a dead stop. It hesitates an awful lot in the lower gears, and when I punch the accelerator at speed. I figured that was normal. Some of the reviews from back when it was introduced make similar criticisms. Now I'm hoping there's a lot more potential in there once I get this intake manifold issue resolved. I would love to know how the actuator arms sit in yours. I'll take some pictures of mine today and post them for an easy comparison.

 

I don't really beat on mine because I'm deathly afraid of it breaking

I have never nailed it to the floor on take-off but I can tell you it has the same torque and launch as my trucks with 7.8L Chevy Big Blocks and that's very impressive for a 4.2 that gets 20MPH. It is about twice as ballsy as my A6 3.0.

Your sure to see a huge difference when you sort out all the issues. That car should be a wicked beast. Just keep in mind parts are expensive and the car is old. Beating on it is for deep pockets only!

BTW How many miles on it?

 

I just bought it - it has 96,000. The car is in fantastic physical shape (condition wise) and appears to have been well-taken care of. Good vehicle history with a lot of maintenance records (though none that help me with this issue). My hope is that it has a few issues that the previous owner just didn't have the time or patience to deal with. I'm prepared to spend some money keeping it up.

So when your engine is off, are both changeover valves inflated, with the arms in resting position?

 

I'll go check. I'll get back to you in a few.

 

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It seems that the upper is partially inflated and the lower is more inflated than the upper with engine off. I can see how they would fail, I think Audi rubber is real rubber not as synthetic as other manufacturers and prone to deteriorate over time. That's another thing always replace every rubber seal and gasket you come close to while you have the chance or you will be back sooner than you think.

BTW if these are disconnected in any way your sure to have a major power loss.

 

Audi plastic, like plastic on all German cars, is made from recycled materials. Thats why it fails. But, you are saving the earth, somehow, by replacing one set with another set! Don't you feel better, now?