tester123

That's the thing, I just replaced it last week with this one:
http://www.amazon.com/gp/product/B0042VVKZ2

Apart from price difference, I can't see any difference. Also, the old one (with my mutilation) was sucking in air just like this and made noises as well. Replaced it since I tore the diaphragm.

You mentioned that your new one stopped the noise. I wonder if it is different from the one I bought. Will try to get OEM one from the dealer and see if that makes any difference.

tester123

Now that brakes and steering issues are resolved, I am back to tackling this stubborn lean codes issue again.

Like I mentioned, the PCV or that disc looking breather valve or whatever the heck it is (wish Audi wouldn't just call it "Valve") is replaced from -out of all the places- Amazon.com! Ok, not so bright perhaps on that decision but, speaking with my local reliable parts supplier, he mentioned that if it has Audi/VW logo, it would have to be OEM and the one from Amazon has those logos like the original one. As the previous one was shot, it wouldn't make any noises. This new one makes womp womp type sound during cold start (more pronounced) and during running, could still hear it sucking air making that noise lightly.

Today, went to a local repair shop and the tech told me that there is too much vacuum in the manifold as the oil cap is hard to twist / remove and sucks ton of air after removing it. Engine doesn't seem to stall per say but, there is lot of air intake when oil cap is open. Reading from other posts, many mentioned that it is that Disc like PCV valve - which is replaced; still this issue remains. He mentioned that before we do any other smoke test / vacuum related work, we should rectify this situation.

My problem is that visually, and twisting etc., the hoses and related plumbing looks intact. Also, checked the "suction valve" or "suction jet pump" and hoses etc. look good and no visible cracks etc. on that thing. It's a $30.00 part so, probably will replace it just to "feel better". Is there a procedure to check this thing or its mode of operation?

What I would like to know is if this PCV valve I got is working (let's say since it is new), what other components could cause oil cap to stick and generate such vacuum in manifold?

Just to add, I removed the battery when tightening the steering bolts and it may have reset the adaptation etc. and the car was much quicker and had little bit more power. However, few mins into a short drive, the CEL came back and engine sluggish again -still drivable but, can tell there is slight sluggish feeling / lag. Climbing uphill, it seems to shudder slightly if more gas is not given...

I think that's about it (as I can think)... Please, share your thoughts and insights.

And of course, Thank You for reading my novel!

nirrozero@gmail.com

it just drives me nuts,

causes cel to show up. mass air flow reading is the same something around 4.5

all my lines are new. im thinking of pulling the manifold and putting silicone around the intake gaskets.

if that doesn't fix it. im suspecting the vacuum actuators in the front.

Prospeeder

If your getting a Load calculation implausible along with lean codes, its the maf sensor. that is one of the only ways the ECU, and the ABS/Traction system calculate engine load for some reason. I usually see lean codes, and then if the customer keeps driving it for a few weeks/months it develops the load implausible code.

tester123

I've been reading about the MAF could do this and during the diagnostic procedures (as per Bentley) the readings out of MAF are within the spec. I'd hate to fork over the money for new MAF and still have the same issue. That's why I am trying to find out if there other things that might have been overlooked.

If it keeps coming back with both lean and load calculation codes, I'll bite the bullet and get a new MAF but not without ruling other things out first.

On the same note, any idea if the oil cap should be tight when engine running? I am get mixed signals from different threads. Some say it is normal and some suggest bad PCV. This flying saucer looking PCV is new so, I am struggling to narrow the problem.

_Adrian_

Have you checked the brake booster ??
It's not common failure but i did encounter some failed units that cause a CEL.

Prospeeder

oh yea forgot about that. Just had a 2.7T A6 come in with lean codes and a brake booster mechanical failure code and it was the booster. If you have a scan tool, watch fuel trim, and hit the brakes a few times, does it suddenly try to add more fuel? Than the booster is bad.

tester123

I'll dig around but off the top would you know what groups to check for fuel trim? I got VAG-COM so, no problem there.

Have not looked into the brake booster section at all. Will do so soon.

markcm

I see this thread is a bit stagnant but there was no resolution posted and I think my reply may be useful for others who stumble upon this thread looking for help.

I was recently fighting lean codes on BOTH BANKS of my 99 A6 with 2.8. It has 200k with the original o2 sensors so I figured replacing those would fix my fuel trims which had recently just jumped to -22%; my plugs were chalk white on all six cylinders. I installed new o2 sensors and saw no change so next I watched my MAF readings and they seemed reasonable (about 4.5g/s at idle and about 130 pulling hard).

Next I guessed an air leak. I built a smoke machine from a tin can with mineral oil in it, a glow plug to heat it, creating smoke, and two air chucks, one connnected to my compressor and the other to my intake maniford (I pulled the line from my Fuel pressure regulator to connect to, pushed about 3psi of air through it into the manifold with the intake blocked at the MAF and look for leaks; it will leak through the valves of course but this still works really well.

It appears I had a visually good yet leaking suction pump. P/N 058133753B which has been superceeded by 058133753d due to common failures in the original.I read many threads about failing suction pumps but not many (if any) peg the symptom of Lean fuel trims on both banks. Considering the suction pump is plumed to the throttle body and there is manifold vacuum in the suction pump I think it's safe to assume a leak here could/would cause lean conditions along with poor idle and/or other related symptoms.

Since I just discovered this leak last night, I cleaned the body of the suction jet pump and then coated the seamed area where it was leaking with silicone and let it dry overnight. My fuel trim was >-20% when I left for work this morning and after 25 miles to work it had dropped to about -7% which is in spec. With this in mind, it appears that my suction pump was leaking just enough air to cause lean conditions, I had spark knock, and a slightly rough idle.

I post this for other VW/Audi owners who are experiencing lean fuel trim on both banks and cannot find any leaks in their vacuum hoses, consider your suction jet pump, they are well known for pluging (which causes the PCV system not to function, building pressure under the valve cover and promoting the o-so-common leaky cam tensioner seals), or falling apart in two pieces and it appears mine simply split and leaked without any visual signs.

Another consideration if your suction pump doesnt fix the lean on both banks issue, fuel injector seals dry out and harden over time, these are less than $1 each and fairly easy to replace. This is less likely since we are talking about lean conditions on "both" banks but I will discuss just in case. There are several ways to test before pulling your injectors, you can squirt water at the base of the injector while the car is running, squirt enough that it pools in the small recession in the manifold where the injector enters; if that water get's "drawn in" to the manifold, its becasue you've got leaky seals. If you change these, blow it out with air before pulling the injector incase theres any sand sitting at the base of the injector, you don't want that sand to fall in the manifold when you pull the injector.

tester123

Thanks "markcm"! Yeah this thread is old and I have been trying to solve this without going to a "doctor" :-)

It's been a bit cold and other obligations have taken priority.

One question is why would the "startrek enterprise" looking PCV valve make the 'womp womp..' sound? It is more pronounced when engine is under load i.e. climbing uphill etc. and that sound is present even at highway speeds although it would more straight sound rather than intermittent.

To me, this sounds like it is pulling outside air through the diaphragm inside the pcv valve and it makes that noise. But the question is, why is it pulling air through this PCV valve? It seems like there is too much vacuum in the intake manifold? or where the bottom of PCV valve connects to and it is being relieved by pulling air through the valve. Tell me if this assumption is wrong.

Also, I tested the mode of operation on a NEW "suction valve" by blowing air in all three openings and compared that with the old one in the car. The old seems to operate in a similar if not, same manner. Plus, there are no cracks etc. on the old one either. So, I am now confused if I should replace this and it would it do any good.

Still, the fuel banks are lean and I am strongly inclined that this vacuum issue(s) surrounding the PCV valve are related. The other vacuum hoses are all replaced with new hoses so, I don't think the gremlin is there.

Please share your thoughts.