Is emissions workshop light an mot fail?

londonTiger

Hi I have been getting intermittent emissions workshop light coming on in the golf for the last few weeks. I don't know why, the mpg is normal so didn'tthink much of it.

Mot is due in a weeks time so want to get it tested soon, iI'm curious will it fail the mot if it has the warning light or will the emissions be determined by the probe test?

The fault code reader says control limit reached at the lambda so there is too much oxygen in the post cat lambda.

I had a probe round and saw that the pre cat lambda is loose. I could unscrew it with my finger. So was wondering if that was causing an air leak which was allowing air into the system. I have tightened it back up

Obviously I will know for sure in 2 or 3 weeks time whether that fixes the fault light. But with the mot due soon the emissions light might come on during the test of I didn't fix the problem

bobbymotors

Take it out, clean it, put some thread lock stuff on it and screw it back in

bigjl

Chuck some CataClean in there.

Follow the instructions rather than just chucking in and hoping for the best.

If the emissions light is coming on then it is not likely to pass the MOT emissions test imho, if it is a petrol that it which I assume it is

mrmot

The warning light is not a fail. I tested a Skoda a while back with the light on and that had emissions that were the best that I've ever seen on a test.

It seems like you've found the cause of the problem and rectified it. Be careful about using sealers and such close to Lambda probes as if they contain Silicones they could contaminate the probe.

arcon5

You dont need thread lock on it ! Just fasten it up, probably wasn't tightened fully many moons ago

On the exhaust system more likely let gasses out than suck air in.

tberry6686

Do not put thread lock on it. Probably the stupidest thing you can do with a lambda sensor. They will normally be in place for years and are often in places with poor access for a spanner making them a pain in the backside to replace without threadlock on and an absolute nightmare with it. Instead put a smear of anti sieze on the threaded section and don't over tighten it, finger tight and a quarter - half turn with a spanner is more than enough.

londonTiger

arcon5 wrote: »

You dont need thread lock on it ! Just fasten it up, probably wasn't tightened fully many moons ago

On the exhaust system more likely let gasses out than suck air in.

I think it unfastened itself because the cable is so rigid and it was twisted as it was tightened. the cable unscrewed the lambda sensor by untwisting itself.

The car failed on the emissions, CO too high. results below. Is this solvable with cataclean? I really dont want to deal with the stress of getting this expensive repair done which will ultimately mean scrapping the car and buying another.

edit: can't upload anywhere, looks like forum image share sites and closing down left right and center.

Last years MOT

Fast idle test
Engine speed: 4250-4850rpm
CO: 0.295% (pass threshold 0.3%)
HC: 41ppm (pass threshold 200ppm)

Idle test
ENgine speed 590-960 rpm
CO: 0.074% (pass threshold 0.5%)

This years MOT - fail

Fast idle test
Engine speed: 4250-4850rpm
CO: 0.382% (pass threshold 0.3%)
HC: 59ppm (pass threshold 200ppm)

Idle test
ENgine speed 590-960 rpm
CO: 0.306% (pass threshold 0.5%)

bigjl

londonTiger wrote: »

I think it unfastened itself because the cable is so rigid and it was twisted as it was tightened. the cable unscrewed the lambda sensor by untwisting itself.

The car failed on the emissions, CO too high. results below. Is this solvable with cataclean? I really dont want to deal with the stress of getting this expensive repair done which will ultimately mean scrapping the car and buying another.

edit: can't upload anywhere, looks like forum image share sites and closing down left right and center.

Last years MOT

Fast idle test
Engine speed: 4250-4850rpm
CO: 0.295% (pass threshold 0.3%)
HC: 41ppm (pass threshold 200ppm)

Idle test
ENgine speed 590-960 rpm
CO: 0.074% (pass threshold 0.5%)

This years MOT - fail

Fast idle test
Engine speed: 4250-4850rpm
CO: 0.382% (pass threshold 0.3%)
HC: 59ppm (pass threshold 200ppm)

Idle test
ENgine speed 590-960 rpm
CO: 0.306% (pass threshold 0.5%)

Extremely likely.

Car Mechanics mag did a feature on CataClean a few years ago using a vehicle with an MOT fail due to emissions and it was sorted with one application.

Cleans the lambda aswell as the Cat itself apparently.

I have used it a few times, to keep diesels used round London all the time as clean as possible.

londonTiger

Phew, it passed after dosing it with cataclean

I've done 70 miles in the car after putting cataclean in it, various people on youtube say that their p0420 code cleared aftering using cataclean after 200+ miles. So maybe the cataclean will keep on working it's magic and clear the catalytic convertor even more.

The p0420 code still comes up though, I reset it before taking it in for mot both times, so time will tell whether the cataclean will fix the problem enough for the cars ECU to be happy with.

This years MOT (attempt 2) - pass

Fast idle test
Engine speed: 4250-4850rpm
CO: 0.247% (pass threshold 0.3%)
HC: 49ppm (pass threshold 200ppm)

Idle test
ENgine speed 590-970 rpm
CO: 0.237% (pass threshold 0.5%)

mcjordi

dont bank on the cataclean turning the light off.. it might do but in my experience it didnt.. however cataclean did bring my emissions back into a mot pass range when they were rather high.
share your experience on the cataclean fb page and they may send you another bottle for free.. they sent me a couple of bottle for leaving a review

facade

It had probably been running rich because of the leak at the pre-cat sensor, and sooted up the catalyst.
Simply running it to get the catalyst really hot would have cleared it anyway.

My car failed last time on excessive CO, so the tester simply left the stick on the accelerator for a few minutes with it revving like fury, then retested it and it passed. Too many short journeys apparently.

(I'm not a fan of magic fluids)