VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading

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Thu 9 Mar 2023 20:47
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - FiestaOwner

My dad's Golf 1.5 TSi passed it's MOT today. He was concerned that the emissions print off showed the Lambda reading at 1.027 (limit being 1.030). Last year it was reading 1.024

The car has done around 25,000 miles. He is worried that it will fail next year's MOT on emissions. Should he be worried about an expensive repair?

Is there anyone (particularly anyone in the trade) who can advise?

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Thu 9 Mar 2023 21:07
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - elekie&a/c doctor
The differences between those readings is marginal. Could even be a slight variation in the gas analyser tester . Worry about it next year.
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Fri 10 Mar 2023 07:13
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - RichardW

25k in 5 years? I suggest you borrow it, fill it with super, and give it an enthusiastic work out!!

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Fri 10 Mar 2023 22:04
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - FiestaOwner

Thanks "Eleckie" and RichardW for your replies.

Dad emailed the VW specialist that did the MOT today. They advised him not to worry about it, but to give the car some decent runs before the next MOT. Think some super unleaded beforehand is a good call too.

Incidently, have had experience of a Kia Pride failing on emissions at one MOT station, then driving to another one, and it passed (This was around 1995).

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Fri 10 Mar 2023 22:32
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - bathtub tom

Incidently, have had experience of a Kia Pride failing on emissions at one MOT station, then driving to another one, and it passed (This was around 1995).

I had one of them and the MOT station took it as a personal challenge because they had to get the emissions test manual out for it each year. It had the filthiest emissions of any car they tested,but it was within the prescribed limits for the model. I suspect the MOT station that failed yours weren't competent.

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Tue 14 Mar 2023 16:27
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - Railroad.

Using a scantool I'd check the long term fuel trim figures to see if over the longer term the ECM has been compensating for a rich or lean running condition. Lambda 1 is the chemically correct air/fuel ratio of 14.7:1. Below 1 indicates a rich condition and above 1 is lean, with anything below 0.97 and above 1.03 being an MOT failure. Ideally you should read 1 on the lambda test, so a figure of 1.027 means you're running lean. The ECM is probably adding fuel to compensate for this, but it would seem you have something wrong such as a vacuum leak or misreading oxygen sensor.

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Tue 5 Mar 2024 17:46
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - FiestaOwner

Though I'd give an update as a year has passed since I started this thread, and the Golf has just passed another MOT.

This year the Lambda reading was much healthier at 1.002

No work has been done to the car, since the previous MOT (not even an oil change).

The last couple of fills have been with super unleaded.

The past 3 weeks the car has had some longer runs (only around 15 miles though). Also, during the same time, my dad has tried to cruise in 5th gear (rather than 6th). The revs have been around 2400 max.

I've seen the term "Italian Tune Up" mentioned on this forum to solve exhaust emission issues. To me, this implies thrashing the living daylights out of the car. This car has never been thrashed.

This years MOT was done at a different MOT station, so it might be down to something as simple as a different exhaust gas analyser, Or, perhaps the test was carried out on a hot engine this year and a cooler one last year?

In any case I'm glad there wasn't any issues.

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Tue 5 Mar 2024 23:26
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - Andrew-T

Also, during the same time, my dad has tried to cruise in 5th gear (rather than 6th). The revs have been around 2400 max.

I've seen the term "Italian Tune Up" mentioned on this forum to solve exhaust emission issues. To me, this implies thrashing the living daylights out of the car. This car has never been thrashed.

Once or twice I have been a passenger with a driver who preferred to keep the revs to the absolute minimum, presumably in the belief that was the most economical thing to do - usually without labouring the engine, but I always felt that was not far away. I don't believe in thrashing a car either, but I try to use every gear somewhere near the 'sweet spot', which is usually pretty clear if the engine is not swamped by an ICE system ....

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Wed 6 Mar 2024 21:19
VW Golf 1.5 TSi 2018 - Exhaust Lambda Reading - FiestaOwner

Also, during the same time, my dad has tried to cruise in 5th gear (rather than 6th). The revs have been around 2400 max.

I've seen the term "Italian Tune Up" mentioned on this forum to solve exhaust emission issues. To me, this implies thrashing the living daylights out of the car. This car has never been thrashed.

Once or twice I have been a passenger with a driver who preferred to keep the revs to the absolute minimum, presumably in the belief that was the most economical thing to do - usually without labouring the engine, but I always felt that was not far away. I don't believe in thrashing a car either, but I try to use every gear somewhere near the 'sweet spot', which is usually pretty clear if the engine is not swamped by an ICE system ....

His driving is fine. He never labours the engine, although he does drive with economy in mind.

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