Emissions MOT Failure

[Lemon S3]

Need some help peeps. Took my car for an MOT on wednesday and it failed on exhaust emissions lambda reading after 2nd fast idle.
They said your lambda sensor must be faulty, so I changed it, £70 later, re test today and it failed again, same thing but was even worse. It has to be between 0.970 and 1.030, the first time it was 1.251 and the second it was 1.312. So its obviously not the lambda at fault. Im a bit stumped (****** off) as to why its over fuelling.

I did a scan on my vag com lite and got the following codes:

VAG-COM Version: Release 409.1-US


Chassis Type: 8L - Audi A3/S3
Scan: 01,02,03,08,15,17,22,35,37,45,54,55,56

-------------------------------------------------------------------------------
Address 01: Engine
Controller: 8N0 906 018
Component: 1.8L R4 5VT 0003
Coding: 05610
Shop #: WSC 12856
5 Faults Found:
17952 - Angle Sensor 1 for Throttle Actuator (G187): Signal too Large
P1544 - 35-10 - - - Intermittent
17580 - Shareware Version. To Decode all DTCs
P1172 - 35-10 - Please Register/Activate - Intermittent
17956 - Shareware Version. To Decode all DTCs
P1548 - 35-00 - Please Register/Activate
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
16885 - Shareware Version. To Decode all DTCs
P0501 - 35-10 - Please Register/Activate - Intermittent
Readiness: 0000 0000

-------------------------------------------------------------------------------

The second code P1172 isn't on the ross tech site for some reason so can't be certain what that is, but think its Angle sensor 2 for throttle actuator - signal too low.
The third code P1548 is the N75, but that is because i had it unplugged at one stage.
The last code P0501 is to do with the speed sensor but thats because i had the fuse out for some reason.

Im not sure what the first code means, is it to do with the throttle body? Also if the second code is the same as the first but signal too low on angle sensor 2, how can one be too large and the other too low?
Also my car is not boosting over 10 PSI, where it used to be 15.

Any advice would be appreciated as this car is starting to pee me off.....again.

 

[jojo]

Was your car upto temps for the emissions test? I always take my car for a blast on the way to the MOT station, specifically doing a 3rd gear run to the redline, warms the cats up nicely and removes any crap in the system.

 

[<tuffty/>]

Haven't you recently fitted a hybrid and larger injectors? Have you had the car mapped since fitting this stuff?

<tuffty/>

 

[beachbuggy]

Had exactly the same issue with mine last week! I spent about an hour with friendly mot man , trying to get it through the emissions. I put it down to hybrid, injectors and sports cat. I managed to get lambda in limits but it threw the co2 readings.

Limit I think is .097 and 1.03 . .97 being rich. With 1.3 that's lean.

In the ended I put stock injectors back in and a stock map, with n75 unplugged and it went straight through. This is on a wideband ecu
id suggest it's your map, especially on an APY which is narrow band.

 

[<tuffty/>]

Welly had issues with his emissions when he deleted the N249 and N112 and didn't leave the valves electrically connected...

Refitted valves and all was good...

<tuffty/>

 

[Lemon S3]

Was your car upto temps for the emissions test? I always take my car for a blast on the way to the MOT station, specifically doing a 3rd gear run to the redline, warms the cats up nicely and removes any crap in the system.

Yeh it was well up to temp, MOT centre was about 10 miles away.

Haven't you recently fitted a hybrid and larger injectors? Have you had the car mapped since fitting this stuff?

<tuffty/>

No everything is standard a part from a large port head.

 

[Lemon S3]

Had exactly the same issue with mine last week! I spent about an hour with friendly mot man , trying to get it through the emissions. I put it down to hybrid, injectors and sports cat. I managed to get lambda in limits but it threw the co2 readings.

Limit I think is .097 and 1.03 . .97 being rich. With 1.3 that's lean.

In the ended I put stock injectors back in and a stock map, with n75 unplugged and it went straight through. This is on a wideband ecu
id suggest it's your map, especially on an APY which is narrow band.

So its not over fuelling, its not enough fuel? The guy that MOT'd it was adamant its over fuelling, plus it does seem to be drinking quite a lot.

Welly had issues with his emissions when he deleted the N249 and N112 and didn't leave the valves electrically connected...

Refitted valves and all was good...

<tuffty/>

I have recently deleted those valves but left them electrically connected.

 

[beachbuggy]

Unless there machine is different . 1.3 is lean. Ie 1.3 parts of air to 1 part of fuel. ( stoich 14.7 = 1 Lambda / stoich 12 = .85 lambda etc etc ) Someone may tell me different but mine at my mot station mine was 1.05 which was outside the limit and lean.

 

[badger5]

>1 is leaner than stoich
<1 is richer than stoich

 

[Lemon S3]

Unless there machine is different . 1.3 is lean. Ie 1.3 parts of air to 1 part of fuel. ( stoich 14.7 = 1 Lambda / stoich 12 = .85 lambda etc etc ) Someone may tell me different but mine at my mot station mine was 1.05 which was outside the limit and lean.

Isn't 14.7:1 for NA cars?
Is 12:1 best for turbo'd applications?

 

[Lemon S3]

>1 is leaner than stoich
<1 is richer than stoich

Just to confirm, my car is running lean then?

 

[beachbuggy]

Isn't 14.7:1 for NA cars?
Is 12:1 best for turbo'd applications?

12:1 is good for turbo cars when ON boost, the rest of the time they are ineffect n/a cars and thus in the cruise should run around 14.7.
Like I say, unless someone corrects me, because Mot machines are different then you running 1.3 is lean yes.

 

[666markyboy]

when did you last change the oil ?????? i've seen cars fail emissions just from having crumy oil in them...... quick oil and filter change and they sail through... just something to think about

 

[Lemon S3]

when did you last change the oil ?????? i've seen cars fail emissions just from having crumy oil in them...... quick oil and filter change and they sail through... just something to think about

Changed probs about 100 miles ago, running 10w40 mineral oil atm due to bedding new rings in.

 

[Lemon S3]

The guys at my old work seem to think its lean as well and that the throttle body is probably open too much. I believe I need to do a TB reset, but don't know how i go about it. Can I do it on VCDS lite?

EDIT: Found out how to do a TB reset but cant do it on VCDS lite

 

[Lemon S3]

Got back from Rhodes on sat and went to a guy on here with a full version on vagcom yesterday to perform a TB reset (thanks Iain, RallyX). It did seem to drive better after it was done and thought it had sorted my problem, took it to have another MOT and yet again it failed. Emissions on the first test was 1.4, so its got even worse somehow, the second test though it came down to 1.18 but still a fail. I really do not know whats going on, starting to really irritate me.

 

[s33nyboy12]

Serious bad luck!

Just going to say and I'm waiting to be shot down here............. I failed on emissions with my a4, forte engine treatment and a blast down the road, took it back and passed! This was a suggestion by the garage doing my mot

 

[Lemon S3]

MOT passed!!!!

Turned out to be the map, as i suspected its had a Revo trial on it in the past which when they revert back, its actually worse than it was before the trial map was put on it. Got a stock map put on it yesterday and it drives soo much smoother and is a crap load quicker too. Took it to get the emissions checked today n it started at 1.089 n thought crap its still going to fail but it gradually went down and with literally a second left on the timer it went to 1.029 n i was soo fricking relieved.

Now to Remap it Think ill end up doing that later today or tomorrow.

 

[s3dave]

Is this why they have stopped doing the trial..