stellick

Hello!

I just recently bought a 2000 A6 2.7t, with 6 speed. Car has 175k miles on it, but it appears to have been very well maintained.

I don't have a Bentley yet, so I was hoping you guys/gals might be familiar with these problems...

I bought it with the CEL on. So I got a scanner and pulled these codes:

16684 - Random misfire
16685 - misfire cyl #1
17521 - Bank 1 sensor 1 (pre-cat o2) internal resistance too high
17539 - Bank 2 sensor 2 (pre-cat o2) internal resistance too high
17927 - intake camshaft contr. bank 1 malfunction
17930 - intake camshaft contr. bank 2 malfunction

I cleared all the codes, and drove her abour 60 miles and the CEL came back on. Pulled the same o2 sensor codes, but nothing else (so far)

What is the likelyhood of both sensors being bad (high mileage they could be bad!)
Is it more likely something else is causing a false reading pre-cat? MAF?

What on earth is the intake camshaft contr. alluding to? Sounds like this could be a huge problem... ??

Thanks for any and all help/info!!

jseklund

With this kind of mileage and no idea of what has been done for maintanence - there could be a few things going on here.

You can do a test on the O2 sensors - go to the tech section and look up "Understanding Oxygen Sensors". With this high mileage, they very well may both be bad if they are originals.

It may also be worth it, since the car is new, to put new spark plugs in and at least know that those are fresh. They may not be the cause of any issues, but at least you'll have a starting point for them.

The cylinder 1 misfire could be caused, IMO, by a bad spark plug, a bad coil pack, a failed O2 sensor (but I would think this would cause problems on the entire bank/random), bad power output stage (again, more likely for an entire bank), bad fuel injector, low fuel pressure (again - more likely for the entire bank), or a bad hall sensor (again- more likely for the entire bank).

The codes about your intake cam controls, I believe, reference your hall sensors. It sounds like they could both be bad, if you treat the codes as a shopping list, which I wouldn't do. These are not a big deal to change out, but may effect driveability. I BELIEVE the codes MAY be caused by the misfires, which may be caused by other things. So I'm not sure if these 2 codes are a cause or effect - I'd fix the other items and then see if the codes come back.

Also, check the wiring to each sensor. It is a circular, metal looking piece that is attached to the front of the passenger side and the rear of the driver's side heads. It has a plug attached to it (or should) and 2 hex head bolts holding it onto the head.

4Driver4

I wouldn't drive that car ten feet until I verified cam timing. Both cam positions sensors bitching means something is out of time. You might want to consider doing a full timing belt service at the same time.

As for the OXS codes (a minor issue compared to the cam thing), I'd just replace both sensors.

stellick

4driver4,
Wouldnt there be larger issues, or at least something more noticeable if my cam timing was off at all? I'm not sure of the adjustability of the cam timing on these beasts, in fact I wouldn't even know where to start.

The timing belt was done approx 50k miles ago, so I was hoping not to do that job until winter was over (I dont have a garage to work in, its f'ing cold in CO right now)

4Driver4

Not necessarily. You can try to replace the cam position sensors if you want, but the code is out of range, not some sensor internal error. Either something moved under the timing cover, timing was set incorrectly when the belt was last done, or the cams are not timed to each other correctly (chain off a link.

I would not drive the car until the issue is resolved. You will need the locking bar and pin to verify timing belt alignment.

jseklund

Not that I don't agree with you 4D4 - but wouldn't he be seeing misfires on more than 1 cylinder if the timing was off? And if he's already driven 60 miles, isn't the damage done? I mean, he's either got collisions or he doens't, right? Or am I wrong?

Beyond that, not moving the car since a timing component may be out of whack and we don't know what it is can't be argued with....

Also, a little more research indicates that these codes may be thrown when oil pressure falls enough to not allow the cam adjusters to do their thing correctly....did you check your oil? Look for leaks, etc. It doesn't seem to be a big thing on the 2.7T but on the 3.0 there is a service bulletin for this...

4Driver4

The timing can be far enough off to cause the ECU to be unhappy without collisions. The belt has to jump about 3 teeth to create ugliness.

Not sure about the misfires. It really depends on what happened.

Also timing could be right. I'm just saying that these codes on my car would be enough to get me out from behind the wheel and under the hood until I was at least able to locate a cause.

stellick

I'll have to double check my oil, I did notice a smell of burning oil this morning, but saw no oil under the car or on anything visible chassis-wise. The cam chain adjusters run via oil pressure then? I'll have to see if there is a pressure leak on them somewhere. So they must also have a pad that can wear out (to guide the chain as pressure is "adjusted") is this easy enough to check them? Pull the valve covers and look at them? Also will have to check the actual electrical connection too.

I'm pretty certain that I've had no collisions in the valve train/pistons etc. The car just would not run the way it is if there was a collision. It idles very smooth and accellerates pretty well - but there IS some random hesitation from time to time. I haven't driven it enought to figure out exactly what/when there is hesitation.

If the timing belt jumped even one tooth, wouldn't that be bad enough to make the car run horribly bad?

69gaugeman

I did a head replacement once and the cam chain was off by one tooth. It idled fine and ran with full power but would get random misfires occasionally. Fixed the chain problem and all was good.

The oil smell is likely the valve cover leaking.

You can do a quick spot check of the timing without the bar and pin by using the pointer on the crank pulley and removing the valve covers. There are timing marks on the bearing caps and cams for timing. It will tell you if you are close or not.

Note I would not set timing this way but it will tell you if there is a problem.

stellick

I guess if the codes I'm throwing say that the "intake camshaft contr." has a malfunction on BOTH BANKS, logically it could mean that the chain has jumped a tooth, or wasn't set right. It could also mean that the chain is still on the right teeth, but the tensioner itself on one bank or both could be faulty. But why would that happen on both banks of cams? Wouldn't that lead you to believe that the timing belt itself is wrong, affecting both banks of OHCs?

Either way, that could cause the misfires that were reported, correct?

Would you mind explaining the "spot check" you mention for the camshafts/bearing caps and the crank pulley? I'm guessing you set the car to TDC via crank pulley. Open valve covers and inspect the cam timing marks. I've looked at the up close pictures of the cams in this: https://www.audiworld.com/tech/eng107.shtml

But I just don't see how the marks on the bearing caps could show me that the chain is off?