MOT Fail

[Siondc]

So my car failed it’s MOT on the emissions. I serviced it 2 days before and ragged it to the garage. It’s an AMK on 145,000. The results were:
Fast Idle
Engine speed:
Limit 2500-3000 Actual 2820
CO:
Limit <0.3 Actual 5.1
HC:
Limit <200 Actual 188
Lambda:
Limit <0.97-1.03 Actual 0.87

Second Fast Idle
Engine speed:
Limit 2500-3000 Actual 2540
CO:
Limit <0.3 Actual 4.3
HC:
Limit <200 Actual 257
Lambda:
Limit <0.97-1.03 Actual 0.89

Natural Idle
Engine speed 760
CO:
Limit <0.5 Actual 1.5

I cleaned the pre cat lambda 2 days prior as this caused it to fail on the same things last year. Could it be that the lambda sensor needs replacing and if so what’s causing this problem to reoccur? Are there any other problems that could cause such high readings? Any help is greatly appreciated.

 

[<tuffty/>]

Fault codes?

<tuffty/>

 

[Siondc]

Fault codes?

<tuffty/>

Haven’t had it scanned yet, waiting to hear from a mobile guy to come and scan it.

 

[Stuart B]

You own an audi s3 without the ability to scan for faults? Jesus.

 

[Siondc]

You own an audi s3 without the ability to scan for faults? Jesus.

Hahahaha yea stu, I don’t know how I’ve survived for so long. What’s the best way to scan then? I know of vcds lite but that’s limited isn’t it? And I don’t want to pay £200 or whatever ridiculous amount it is for the the full thing.

 

[Stuart B]

Vcdslite shows faults for free though. So for £5 you can save yourself time a money. I cleared about 20 faults from my TT yesterday. No EML no particular misbehaving.

 

[Siondc]

So I buy a cable off eBay, what site can I download it off then?

 

[<tuffty/>]

So I buy a cable off eBay, what site can I download it off then?

From the FAQ's in the stickies...
https://www.audi-sport.net/xf/threa...lp-please-read-before-posting-updated.168407/

<tuffty/>

 

[Siondc]

cheers.

 

[Tj 0785]

Hahahaha yea stu, I don’t know how I’ve survived for so long. What’s the best way to scan then? I know of vcds lite but that’s limited isn’t it? And I don’t want to pay £200 or whatever ridiculous amount it is for the the full thing.

How much do you pay for your scans? £30-£40 roughly? Get car scanned 4/5 times(with an s3 could be anywhere from 1 or 5 years)
Which is money you won’t get back but a cable and you will always be able to sell it for Close to £180
Not so ridiculous when you think about it!

 

[Retroman]

For the MOT tests:-
High CO is either a very rich mixture or ineffective cat. Your readings are way over the limits and so I would guess a Cat which isn't working at all.
High HC is often an "incomplete combustion burn" so a poor spark is often the culprit e.g. old spark plugs or problem coil/lead
Lambda problems in an MOT emissions test context does not relate to the lambda sensors but oxygen in the exhaust gases outside of permitted limits. Usually an exhaust system leak - exhausts gas pulses suck in air (from leaks) causing erroneous tailpipe emission readings.

Faulty sensors normally trigger a warning light and error code e.g. they get old and react outside tolerance or go completely dead and cause an "implausible" signal.

 

[Siondc]

So I have got myself a cable and vcds lite.
Fault code p1453 exhaust gas temp sensor 1
Guessing that’s the pre cat one? Could this cause such high readings of CO?

 

[scotty_24]

So I have got myself a cable and vcds lite.
Fault code p1453 exhaust gas temp sensor 1
Guessing that’s the pre cat one? Could this cause such high readings of CO?

And there we have the answer!
EGT is the exhaust gas temperature sensor in the turbo hotside. It plugs in under the inlet manifold and the wire travels from under the inlet manifold, around the passenger side of the block to the turbo.
Check its plugged in first of all, as its typically left unplugged by accident if people are working in that area.
If the EGT sensor isn't working, or is miss reading, it will fuel dump and cause the mixture to be super rich.


17863/P1455 - Exhaust Gas Temp Sensor 1 (G235): Implausible Signal
Possible Symptoms

• Malfunction Indicator Light (MIL) ON

Possible Causes

• Fuse(s) faulty
• Wiring and/or Connector(s) from/to Exhaust Gas Temp Sensor 1 (G235) faulty
• Exhaust Gas Temp Sensor 1 (G235) faulty

Possible Solutions

• Check Fuse(s)
• Check Wiring and/or Connector(s) from/to Exhaust Gas Temp Sensor 1 (G235)
• Check/Replace Exhaust Gas Temp Sensor 1 (G235)

Special Notes

• Failure of this sensor in the NAR market BBW 2.0L engine is common. That engine was found in the 2004 - 2005 VW Golf/Jetta/Bora (1J/9M) chassis.

http://wiki.ross-tech.com/wiki/index.php/17863/P1455

 

[Siondc]

I’ve checked the sensor. It’s all plugged in and doesn’t look damaged. Must be FUBAR’d. Where can I buy one apart from Audi? How much are they from TPS?

 

[scotty_24]

TPS is your best bet or Audi. Buy cheap buy twice

 

[Warsuperior]

I bought Carport program, it has same properties as VCDS but lot cheaper
https://carport-diagnostics.com/en
I bought the pro module and have been happy with it.

 

[hydro s3]

Try the parts request on here.

 

[Stuart B]

before you buy anything run a log including the AFR / Lamfa and EGT someone on here recently had theirs unplugged which was "null" under EGT and if it is knackered then it reads 999 - both of which make the car run at 0.75 lamfa which is about 11.5:1
maybe check what readings the ECU is getting from the component as your problem maybe with the wiring not the sensor.

You can even log with Android Torque Pro, it doesn't matter about the readings per second in this case.

EGT Sensors are pretty expensive if I remember rightly.

did you decat your S3?

 

[Siondc]

I tried to resolder the egt sensor but didn’t work so I’m just going to replace it and see what happens. Turns out I have a new fault that I thought I’d fixed but clearly haven’t. My ABS and ESP light have been on for a while and I’ve changed the abs sensor but never got round to clearing the fault (abs sensor near side rear intermittent). I cleared it yesterday and it stayed off, happy days. Got in the car this morning, drive about 100m ESP kicks in and lights come back on, f**k. Every time I start the car now there’s no lights and as soon as I get about 100m it comes back on after triggering the esp. no other faults to be found. Cars doing my head in now.

 

[Stuart B]

Are both lights on? Its usually the lateral or longitudinal sensor.

 

[Tj 0785]

cars
doing my head in now.

Spoken like a true s3 owner

 

[Siondc]

Ha, ****** cars. Now this missus is on at me to get rid of it cos I’m “wasting money”.
Both lights on, that did cross my mind but no other faults other than rear abs sensor, ***.

 

[GeorgieS3]

This happened to me and turned out to be the wheel bearing. Hope this helps mate.