1.4 TSI ACT Failed Emissions - Help

[clarkey1230]

Hi, I’ve had the same problem with 2016 Audi A3 it won’t pass the CO emissions test, what exactly did you replace that fixed this? Just the pre-cat lambda sensor?

Hi there
Did you resolve this with a new lambda sensor too? I have the same issue now

[umairzh]

I just had the same symptoms on my 2015 1.4 TSI COD Q3, and luckily I found your post Thriftmeister. Actually had cambelt replaced at ~39k miles 7 months back and everything was fine. Then an episode of bad fuel (from a shadowy fuel station) triggered the engined management light 2 months ago. Pre-cat Lambda sensor changed after the following diagnosis at 42k miles.

"Road tested the vehicle and confirmed the ecu light on. Performed a diagnostic scan, there are faults for the pre cat lambda slow switching and the system being too lean. Watched live data and confirmed the pre cat lambda is very slow, introduced an air leak and then excess fuel, it switches but not very quickly. Smoke checked the inlet system, ok. Followed the odis test plan and the result is an failed lambda probe, new required." Changed with genuine Audi.

Then all went well until MOT failure at 45k due to emissions (High CO ~ 0.99 at Fast Idle test and 0.92 at Second Fast Idle test).

Took to the same garage where the lambda sensor was replaced. They were unable to find any errors or issues with Lambda sensor. They were thinking a bad injector and were planning to take them out and send them for testing. Showed this post to them, they took the plunge and changed the sensor... and all ok now..... They will ofcourse claim this under Audi warranty for parts, but were really ****** as the odis didnt detect any errors, which now I understand should have been done by the post-cat Lambda......

Anyways happy, as only had to pay for car rental while the MOT failed (on the last day of its validity).

[ss332]

Hello,

I am in a similar boat with my Audi Q3 TFSi (2016) with 26K mileage.

I've Just been back from a VAG specialist and they've a hit a dead end with it even after replacing the pre-CAT lambda sensor with a genuine part (that costed me over 300 quids. &#128577 and yet the CO emissions are exactly same as before at 0.58% (the other HC, etc are also high )

They said it's very highly unlikely that the CAT has gone on such a low mileage (26K miles) so no point in replacing it.

The other alternative was to get the injectors tested in a lab to see which one is faulty that might be over-fueling the engine and causing high emissions.

Any other ideas or conversation you might have had at that time that can help in narrowing it down ?

Thanks,

[Crasher]

Any fault codes? Engine MIL on?

[ss332]

No fault code or lights at the moment. However, There was this Engine MIL light on a couple of month ago and the OBD showed a fault code P2177 - 'Engine too lean on bank side 1' something of that sort.

That fault code was reset by my local garage and since then no light have come up. It was only last week when the MOT failed due to high emissions that the whole saga started and different garages have diagnosed it differently - One saying it's the CAT that's gone whereas a VAG specialist has already changed the pre-CAT lambda sensor (for around 300 quids) but to no avail.

Now they want to test the injectors in the lab to see if anyone is faulty and over-fuelling.

The CO emissions are around 0.5% where the limit is 0.2%.

Thanks,

[Crasher]

What is the VIN?

[ss332]

VIN is - WAUZZZ8UXHR036842

[Crasher]

18609 (P2177) - Bank 1; System Too Lean off Idle: Upper Limit Exceeded

That looks like a small air leak and needs some in depth work such as the automatic test sequence, studying measuring blocks for various signals and the charge air system pressurising to check for leaks, I haven't seen it before on that particular engine but on others it has been a small air leak post Air Mass Meter but the CZEA doesn't have one so it is going to be tricky to find.

[ss332]

Thanks for the reply. The problem is that fault code is no longer there (since reset) and hasn't come up again nor any other lights or fault code. If it was an air leak clearly it hasn't fixed itself bringing me back to square one unfortunately. Not sure which path to really take here (injectore vs. replacing the CAT vs diagnosing the air leak) as each one is a long drawn one (not to mention costly) without any guarantees to fixing the underlying issue.

[Crasher]

If the Co after the cat was circa 0.6% the ECU would pick this up very quickly and bring on the MIL with a code so it makes me suspect the testers machine. If it was here I would run through the full suit of automatic tests in basic settings.