MOT Fail - Emissions Help

[Ian W]

Had my 2001 AMK, (111K) in for the MOT today and it has failed on emissions, don't have the print out sadly but the chap said it failed on all 3 tests and was well off the limits.

Car is running a Pipewerx 3" system with a sports cat that is 18 months old, a new Bosch post cat lambda was fitted at the same time.

Car runs and drives fine, haven't noticed any performance drop or any increase in fuel consumption, no active faults on VCDS.

Any hints on what I should be looking for? I'm sure it is a sensor or something causing it to run rich as it went through no problem last year with the same cat setup and I can't believe it has failed that quickly, from what I have read even without a cat they should be pretty close to the pass limit.

I've seen posts suggesting the temp sensor can cause rich running? I'm not a fan of throwing new parts on without a decent indication of what the source of the problem is but emissions have always been a bit of a mystery to me!

Any help much appreciated!

 

[s3mad_dude]

What were your results? How close were you to passing? I’m assuming the engine was nice and warm when they did the test?

 

[Ian W]

What were your results? How close were you to passing? I’m assuming the engine was nice and warm when they did the test?

Not sure on the exact results as I didn't get a print out but the chap said it wasn't anywhere near close.

The car was warm but I hadn't thrashed it (as was the plan) due to the weather.

I've since scanned the car again and I have an EGT fault, wasn't there last week so either it is intermittent or it's just happened :/ Tried to clear it last night but it comes back straight away.

1 Fault Found:
17861 - Exhaust Gas Temp Sensor 1 (G235): Open or Short to Plus
P1453 - 35-00 -

Based on what I have read so far it certainly isn't as easy as just fitting a new sensor due to supply issues so unlikely I will get my retest within 10 days

I'll be checking tonight to confirm it is plugged in securely, I have no recollection of removing it but worth a check!

 

[s3mad_dude]

Check the wiring too, in case there’s a break in the loom somewhere (I know it’s easier said than done) but if it’s not the sensor then I’m out of ideas. Keep us posted though.

 

[Ian W]

Check the wiring too, in case there’s a break in the loom somewhere (I know it’s easier said than done) but if it’s not the sensor then I’m out of ideas. Keep us posted though.

I've confirmed that it is plugged in, which is what I would have expected.

Part is NLS from Audi so I have bought a second hand one, hopefully get that fitted this weekend if it arrives quickly - if that doesn't sort it then it will on to the loom...

 

[desertstorm]

That will definitely be an issue for emissions. When the EGT fails like that or the temperature exceeds around 940 degrees the ECU goes into engine protection and fuels at 0.75 Lambda instead of 1. It should be a lot more fuel efficient when you get it fixed. You maybe able to fix the existing one there is a very common issue with the soldered joints on the PCB in the black box sensor part.
I fixed the one on my 225 TT with the same fault. Early EGT sensors are potted in a jelly like substance that can be removed . Later ones are potted in a more solid substance that is difficult to remove. Worth a go at looking at . Problem with second hand items like these is that they are 20 years old and possibly will be faulty or intermittent like yours.

Mk1 TT 225 track day car, Officially a ten second car 10.8 seconds at 127 mph.

Having done the odd track day event in my everyday A4 diesel estate decided that it might be a bit better if I have a go at converting a car to a decent track day spec to have some more serious fun. I know lots of people opt for Clios or BMW's but I was never one to follow the crowd. Used S3's...

www.audi-sport.net

 

[Ian W]

That will definitely be an issue for emissions. When the EGT fails like that or the temperature exceeds around 940 degrees the ECU goes into engine protection and fuels at 0.75 Lambda instead of 1. It should be a lot more fuel efficient when you get it fixed. You maybe able to fix the existing one there is a very common issue with the soldered joints on the PCB in the black box sensor part.
I fixed the one on my 225 TT with the same fault. Early EGT sensors are potted in a jelly like substance that can be removed . Later ones are potted in a more solid substance that is difficult to remove. Worth a go at looking at . Problem with second hand items like these is that they are 20 years old and possibly will be faulty or intermittent like yours.

Mk1 TT 225 track day car, Officially a ten second car 10.8 seconds at 127 mph.

Having done the odd track day event in my everyday A4 diesel estate decided that it might be a bit better if I have a go at converting a car to a decent track day spec to have some more serious fun. I know lots of people opt for Clios or BMW's but I was never one to follow the crowd. Used S3's...

www.audi-sport.net

Thanks, i've read your thread, I'm hoping to get mine open this weekend and check for dry joints and all being well repair as you did.

Mine being an early facelift I am keeping my fingers crossed it is in the jelly to make things a bit easier.

 

[Ian W]

I opened up the sensor this weekend, the joints looked ok but we cleaned and re-soldered them anyway for good measure.

No difference sadly so I'm now waiting on the replacement sensor and new PCB to continue fault finding, probably after xmas now

 

[Ian W]

My replacement PCB arrived from http://www.sidmotorsport.pl/ at some point between Xmas and new year, who knows what day it was haha, fitted it on Monday, cleared the EGT fault and it went through an MOT today