Can air inlet leaks cause a lambda VAG-COM code?

[aclwalker 3]

Now that I've fixed my coolant leak and ABS sensor issue, it's time to turn my attention once again to the poor running of my VR6.

 

I replaced my lambda sensor a while back, but had issues with the wiring. One of the wires before had been broken and the plug had been bypassed for this core. I was forced to do the same with my new lambda probe. Initially the car ran great (like I'd never experienced before), but very soon the running issues came back: lumpy idle, wild hunting for 30 seconds after a cold start, hesitation, occasional conking out at roundabouts.

 

I've now re-wired that about 3 times now and it's totally covered in electrical tape and I'm pretty sure that it's good now. It's not ideal, but I'm now not so sure that the problem is the wiring.

 

However, I get the following code in VAG-COM:

 

00537 - Lambda (Oxygen Sensor) Regulation

11-10 - Control Limit Not Reached - Intermittent

 

I never used to get a code at all with the old sensor, but that may just be coincidence. I'm now thinking that me clearing the code is allowing it to run well again for a short time before it notices that there's still an issue. Maybe the old sensor didn't detect the changes as well and hence didn't throw a code when it should have.

 

In the not too distant past I've also replaced all HT leads, the coilpack and most recently all the spark plugs (again) and the issue is still here.

 

I'm actually beginning to think there's an air leak, allowing unmetered air in. I'm not 100% sure, but sometimes I think I can hear a sucking noise if I've got the bonnet up, especially for a second or two immediately after switching off the engine, as everything is coming to a halt.

 

Also on the air inlet, where the smaller pipe (with the dummy sensor (right at the top left-most spark plug)) joins the large diameter main ducting, there's oil on the outside. This seems to suggest that that joint is leaking air.

 

Could this be the cause of my running issues, and of the VAG-COM code above?

 

How much does a replacement for all this ducting cost?

 

One other thing. Once I had the following code in addition to the one above:

 

00533 - Idle Speed Regulation

10-10 - Adaptation Limit Not Reached - Intermittent

 

What I did notice that time was that I had actually forgotten to tighten up the jubilee clip where the MAF joins the ducting. The car ran really badly until I tightened that up, where it improved but still isn't great. This code hasn't reappeared but the first one I can keep clearing and it will always come back.

 

Any help with the following would be greatly appreciated:

 

1 Bearing in mind what I HAVE replaced, do these symptoms sound like an air leak in the inlet ducting? 30 seconds of RPMs hunting on cold start, occasional conking out at junctions, hesitancy, lumpy idle.

 

2 Is new ducting expensive?

 

3 Is it possible to repair the junction where I suspect I might have a leak, with some sort of tape?

 

4 Does the MAF throw a VAG-COM code when it's failing?

 

5 Any way of testing the MAF?

 

6 Could an air leak result in a lambda probe code like I'm getting?

 

Any other help gladly accepted.

 

Cheers.

 

Edit: BTW, I have no cold or hot starting problems. My car has never been difficult to start.