Renault Grand Scenic II 2009 - MOT emission failed by large margine

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Thu 20 Oct 2022 18:04
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Hi,

Today, my car has failed emission test by large margin :( It came as a bit of a surprise as last year everything was well within the limits. Today test results (required norm given in parenthesis):

CO (max. 0.2%) measured 7.28%

HC (max 200pm) measured 495ppm

Lambda (0.97 - 1.03) measured 0.77

My question is, do you think that changing air filter, oil and maybe cleaning air sensor could be enough to bring those measurements back within the limits. Looking how far the numbers are from the norm I'm considering if it is even worth changing oil in this car as I fear it might be going straight to the scrapyard regardless of what I do :(

Edited by Piotr Foltyn on 20/10/2022 at 18:04

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Thu 20 Oct 2022 18:53
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Adampr

The fact you ask the question suggests your air filter is old. I would replace that, chuck a bottle of redex in the tank and take it for a hard drive. If that doesn't do it, you probably need a new catalyst

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Thu 20 Oct 2022 19:08
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Thank you for the answers. The oil and filters were replaced last year so indeed I might give it a go. The car runs on petrol but has been converted to LPG (autogas). I'm not sure if they disable gas installation during test. Will need to confirm with the garage.

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Thu 20 Oct 2022 18:54
Renault Grand Scenic II 2009 - MOT emission failed by large margine - _

Best to do all of the above, won't cost a lot and cheaper than a new car.

Petrol ? Diesel?

Clean EGR?

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Thu 20 Oct 2022 19:12
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Thank you. Originally it was a petrol vehicle but has been converted to LPG. I think I was imagining that if there is a clogged up filter the emission measurements will not change drastically. Seeing CO levels being order of magnitude above the norm got me thinking something serious is broken in the engine.

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Thu 20 Oct 2022 19:37
Renault Grand Scenic II 2009 - MOT emission failed by large margine - elekie&a/c doctor
Changing those parts is unlikely to make any difference. How is the car being presented for the mot , running on petrol or lpg ? This will make a difference to the emission test .
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Thu 20 Oct 2022 20:01
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Assuming they didn't press any buttons to disable LPG, the car starts on petrol and quickly switches to LPG. Last year the same car with same LPG installation in the same garage passed emissions with flying colours :( I'm just baffled what could have caused such a drastic change in emissions.

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Thu 20 Oct 2022 20:36
Renault Grand Scenic II 2009 - MOT emission failed by large margine - elekie&a/c doctor
If it was tested on lpg , then the mot garage needs to do a recalculation of the emission figures . I doubt if this was done . Hc is usually higher on lpg . I guess it’s still running a cat ? Possibly the lpg system needs servicing or present the car running on petrol.

Edited by elekie&a/c doctor on 20/10/2022 at 20:47

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Thu 20 Oct 2022 21:45
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Thank you for suggestions. Yes it runs a cat. I'll disable LPG for the time being and present the car running on petrol on my next visit for the MOT.

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Thu 20 Oct 2022 22:31
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

One more question. What is your opinion on petrol additives like this one:

www.halfords.com/motoring/engine-oils-and-fluids/f...l

It is cheap enough that I'll give it a go regardless but was wondering if people think it is waste of money or a real deal.

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Fri 21 Oct 2022 11:26
Renault Grand Scenic II 2009 - MOT emission failed by large margine - edlithgow
Emissions, mpg and performance are VERY little affected by air filter state until it is so clogged that it is collapsing from internal negative pressure at high power outputs. Your filter is unlikely to be in that state, but if you wanted to eliminate it entirely as a factor in the test, you could do just that, and then put it back afterwards.

I have got a (pre-cat) Renault 5 campus thro an MOT after failing for “visible smoke” by changing the oil, adding Wynns viscosity improver, and cleaning the crankcase ventilator, but I also swapped the MOT tester, probably the most important factor.

I don’t miss the MOT
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Fri 21 Oct 2022 16:26
Renault Grand Scenic II 2009 - MOT emission failed by large margine - bathtub tom
Emissions, mpg and performance are VERY little affected by air filter state

Do modern engines suffer poor MPG from a blocked air filter? I suspect engine controls would limit the fuelling to match the restricted air intake, restricting performance certainly.

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Sat 22 Oct 2022 11:20
Renault Grand Scenic II 2009 - MOT emission failed by large margine - edlithgow
Emissions, mpg and performance are VERY little affected by air filter state

Do modern engines suffer poor MPG from a blocked air filter? I suspect engine controls would limit the fuelling to match the restricted air intake, restricting performance certainly.

No, they don’t. Which is what I said. Max power output would be limited by air supply. Old tech without feedback control is slightly more affected but it takes extreme clogging for the affect to be detectable
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Thu 3 Nov 2022 17:51
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Solution to the problematic emissions turned out to be catalytic converter replacement :( Car passed the MOT and with some other repairs the garage bill came up to £900. Thanks for all the replies.

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Thu 3 Nov 2022 20:01
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Xileno

Thanks for the update. Hopefully it will do a few more years, £900 doesn't feel so bad then.

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Thu 3 Nov 2022 22:28
Renault Grand Scenic II 2009 - MOT emission failed by large margine - bathtub tom

I wonder if the OP bothered to 'weigh in' the old cat to recoup some of his costs?

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Thu 3 Nov 2022 23:36
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

I can ask the garage if they still have my old cat. Although given it is broken, I'm not sure how valuable it is and where to take it - nearest scrapyard?

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Fri 4 Nov 2022 06:21
Renault Grand Scenic II 2009 - MOT emission failed by large margine - paul 1963

I can ask the garage if they still have my old cat. Although given it is broken, I'm not sure how valuable it is and where to take it - nearest scrapyard?

Despite it being broken it is still full of valuable metals, get it back and sell it, bet you get at least £50 for it....keep us informed.

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Fri 4 Nov 2022 08:05
Renault Grand Scenic II 2009 - MOT emission failed by large margine - elekie&a/c doctor
It’s likely the new cat has been supplied on an exchange basis . The old unit goes back to the parts supplier to recover an “old core surcharge “ .
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Fri 4 Nov 2022 10:35
Renault Grand Scenic II 2009 - MOT emission failed by large margine - paul 1963
It’s likely the new cat has been supplied on an exchange basis . The old unit goes back to the parts supplier to recover an “old core surcharge “ .

Doc, surcharge on most cats is only £15., most garages weigh them in for far more.

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Fri 4 Nov 2022 11:00
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

I went to the garage and took my old cat back. Indeed the surcharge was £15 which I had to pay. With cat in hand I went to Nationwide Metal Recycling and got £150 for it! Thank you very much for your comments :)

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Fri 4 Nov 2022 11:12
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Renault Enthusiast

Cost of new aftermarket catalytic converter £300. Labour to replace it £130. Rest of the costs were associated with automatic handbrake diagnostic and repairs. The emissions with new cat are:

CO (max. 0.2%) measured 0.00%

HC (max 200pm) measured 7ppm

Lambda (0.97 - 1.03) measured 1.01

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Fri 4 Nov 2022 11:49
Renault Grand Scenic II 2009 - MOT emission failed by large margine - paul 1963

Well done Renault enthusiast! I make pocket money by paying garages there 15 surcharge then sell them myself ( I'm in the trade).

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Sat 5 Nov 2022 23:09
Renault Grand Scenic II 2009 - MOT emission failed by large margine - Brit_in_Germany

Hence the rash of cat. thefts. There does not seem to be a working system to stop money being made from these thefts.

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