Emissions fail NCT

wonski · 19-06-2020 2:44pm #1

Just got my results and the readings are so high that I don't think the dipetane trick will do:

05 Volvo s40 1.8 petrol with 324k on the clock. Is it the end of the road?

I had it serviced few weeks ago, but haven't changed spark plugs, only oil and filter. It does appear to run rough on idle sometimes, but not like misfiring badly or anything.

Apart from that it only failed on parking brake imbalance and the boot lock started acting again, both easy fixes.

Never ever failed any car on emissions, was spot on until now.

Given the readings I feel it is game over, am I right?

jimgoose · 19-06-2020 3:04pm

It's not game over, far from it. Assuming oil consumption is OK, what you've got there is an engine running waaay too rich. It could be a failed MAF/MAP sensor, or one of a handful of things. A competent mechanic will sort it.

wonski · 19-06-2020 3:12pm

There are no errors on the dash, I assume one of those would trigger check engine light, no?

It drank some oil on the past, but passed emissions with a good margin left. This year no oil loss so I am thinking this could be more serious than just a sensor.

Hope you are right.

Will start from basics new spark plugs, get any error codes read and see if there is anything there... Will drop it to the garage next week. They will be delighted to see it

jimgoose · 19-06-2020 3:18pm

wonski wrote: »

There are no errors on the dash, I assume one of those would trigger check engine light, no?

It drank some oil on the past, but passed emissions with a good margin left. This year no oil loss so I am thinking this could be more serious than just a sensor.

Hope you are right.

Will start from basics new spark plugs, get any error codes read and see if there is anything there... Will drop it to the garage next week. They will be delighted to see it

Failure/misbehaviour of "just a sensor" means the computer is suddenly trying to operate the engine with incomplete and/or incorrect data and so things drift more or less haywire. There are a number of things your mechanic will check, including stored OBD-II/platform-specific fault codes (which may or may not cause a check-engine light), several sensors like MAF/MAP, upstream O2, coolant temperature, etc. You could also have a faulty coil.

wonski · 19-06-2020 3:37pm

I am only worried how much it is gonna cost me tbh...

Thank you for reassurance that it might not be as bad as I thought.

Would be a shame to scrap it tbh... Served, and still serves me well

jimgoose · 19-06-2020 3:42pm

wonski wrote: »

I am only worried how much it is gonna cost me tbh...

Thank you for reassurance that it might not be as bad as I thought.

Would be a shame to scrap it tbh... Served, and still serves me well

I had a 1999 Xsara a few years back that developed a head-melting case of it much like your'n. A new idle control valve and cleaning the throttle body with a toothbrush had it as good as new.

Stoolbend · 20-06-2020 1:22am

Do you hear a hiss when you switch off the engine?

Does it cut out or nearly cut out sometimes?

There is a vacuum pipe that runs behind the inlet manifold that can split.

Mad_Mike · 20-06-2020 2:55am

I'm guessing with high HC figures, it's either a misfire or a vacuum problem.
As you have already said the plugs weren't changed, that would be my first thing to do and see if the lumpy idle is improved.
If not, check all ignition coils too and as Stoolbend says, check for air leaks/split pipes etc.
Also, bring the car to an auto electric place rather than the garage if you can change plugs and air filter yourself
jimgoose is bang on. You need code readings to let you know exactly whats happening

Had the very same issue, but higher figures, on my daughters Grande Punto last October and after hours of head scratching
I finally found that there was no fuse in the fusebox for the O2/lambda sensor since she bought it!

wonski · 20-06-2020 3:22am

Stoolbend wrote: »

Do you hear a hiss when you switch off the engine?

Does it cut out or nearly cut out sometimes?

There is a vacuum pipe that runs behind the inlet manifold that can split.

The opposite tbh. Sometimes it revs higher than it should when idle... No hiss or cutting off at all.

Thanks for the suggestion, but I don't think that's it. Will check anyway, just in case. There is a bit of vibration now and then. The guys I service the car with are very reasonable and "down to earth" guys. They would never charge me for a job they can't do and always mention if they can't guarantee the result or if the labour can't be determined...

The plan is to read the codes. Unless something obvious is showing up do nothing. Change the plugs, add some dipetane or whatever for a start. Drive it for a day or two and then read them again.

Go back for retest and see what happens.

Not great plan, but not going to be trapped into the whole lambda/cat/whatever sensors can be replaced/another garage another idea/ trap.

wonski · 20-06-2020 3:31am

Mad_Mike wrote: »

I'm guessing with high HC figures, it's either a misfire or a vacuum problem.
As you have already said the plugs weren't changed, that would be my first thing to do and see if the lumpy idle is improved.
If not, check all ignition coils too and as Stoolbend says, check for air leaks/split pipes etc.
Also, bring the car to an auto electric place rather than the garage if you can change plugs and air filter yourself
jimgoose is bang on. You need code readings to let you know exactly whats happening

Had the very same issue, but higher figures, on my daughters Grande Punto last October and after hours of head scratching
I finally found that there was no fuse in the fusebox for the O2/lambda sensor since she bought it!

Plugs and coils I can check meself. Oil and oil/air filters were replaced just weeks ago so no point doing that again.

Fuse for o2/lambda sensor is a new one to me.
Wil check all fuses just in case.

That car passed emissions last two years with large margin so doubt it though.

Have a feeling it is oil rings/compression issue after reading a little more online.

Will give all the ideas a go, but will keep an eye on bangeromics thread at the same time

John.G · 20-06-2020 8:38am

As above, definitely renew the plugs and clean the throttle body, also check for any vacuum leaks as 970 RPM seems a very high idling speed.

Stoolbend · 20-06-2020 6:23pm

Leave it ticking over and spray some carburettor cleaner in and around the inlet manifold and see if it changes the tone of the engine.

Does it burn oil?

wonski · 20-06-2020 10:08pm

Stoolbend wrote: »

Leave it ticking over and spray some carburettor cleaner in and around the inlet manifold and see if it changes the tone of the engine.

Does it burn oil?

As for oil burning there was an incident of lost oil, but not recent and it did pass the emissions with flying colours. Didn't need to top up at all last 12 months between services and just put fresh few weeks ago so will take some time to see if the level drops.

No smoke or anything obvious, but the tester mentioned he could "smell" it, so there must be either good amount of u burned fuel or possibly a bit of oil...

I can clean the throttle body meself, have some left over cleaner can from 3 years ago when I was cleaning the second hand one. Won't do harm to try it.

What do you mean by spraying it around inlet manifold? Just spraying it in with air while the engine is running? Never done this, so not sure.

Last year test was idle at 850rpm, strangely the temp was 24 degrees. This time 103 degrees...

Mad_Mike · 20-06-2020 11:01pm

wonski wrote: »

What do you mean by spraying it around inlet manifold? Just spraying it in with air while the engine is running? Never done this, so not sure.

Basically you spray it around the hoses, and if there is a split in the hose, it will suck it in and you'll hear the revs increase in the engine. Great way of finding splits in hoses where you can't see

wonski · 20-06-2020 11:12pm

Mad_Mike wrote: »

Basically you spray it around the hoses, and if there is a split in the hose, it will suck it in and you'll hear the revs increase in the engine. Great way of finding splits in hoses where you can't see

Gotcha

fullstop · 20-06-2020 11:14pm

Is the emisssions test based on what the emissions for the car are supposed to be, or is it the same regardless of model?

wonski · 20-06-2020 11:22pm

fullstop wrote: »

Is the emisssions test based on what the emissions for the car are supposed to be, or is it the same regardless of model?

Depends on the year of manufacture. That's what the report states.

Mad_Mike · 20-06-2020 11:32pm

Taken from the NCT Manual

"Where it can be established that the vehicle manufacturer’s recommendations on exhaust emissions are
higher than those listed in the reasons for failure then the manufacturer’s figure should be the criteria
used when deciding whether or not the vehicle passes."

So my reading is basically you have to pass by the NCT's figures unless the manufacturer reckons it should be higher?

Mad_Mike · 25-06-2020 6:00pm

Any news on this, or did you get any codes read?

wonski · 25-06-2020 8:48pm

Mad_Mike wrote: »

Any news on this, or did you get any codes read?

Was working all week, dropping the car tomorrow morning to the garage.

Have a retest booked for 5th July, so not much time left to get it passed.

Need to pass by 19th...

Will let you know guys

hopefully some good news

Dirty Nails · 25-06-2020 11:06pm

Did you have a look at the air filter?
There might be a dead crow stuck in the intake

wonski · 25-06-2020 11:39pm

Dirty Nails wrote: »

Did you have a look at the air filter?
There might be a dead crow stuck in the intake

Had it serviced few weeks ago... Minor service oil/filters.

I trust the guys would notice one there

Will do the plugs tomorrow, have a spirited drive over the weekend and see if the idling improves.

Unless the ecu throws up something obvious, like a crow stuck in the intake, dead or alive.

Dirty Nails · 26-06-2020 12:11am

wonski wrote: »

Had it serviced few weeks ago... Minor service oil/filters.

I trust the guys would notice one there

Will do the plugs tomorrow, have a spirited drive over the weekend and see if the idling improves.

Unless the ecu throws up something obvious, like a crow stuck in the intake, dead or alive.

I was joking about the crow but a restricted air filter would drive the emissions silly. Don't think any diagnostics have a crow test function

Rule out all the simple things first. Maybe even get the fuel pressure checked before you delve too deep into engine management stuff. Sticking regulators are common,diags won't tell you that.

wonski · 26-06-2020 3:11pm

Got the car back today with set of new spark plugs and a bit of magic liquid added to the tank. Told to drive the **** out of it before the test. Computer diagnostic was waste of time and money, some random misfiring here and there. Nothing out of ordinary.

We will see if it does anything at all.

Bear in mind this isn't going to be DIY thing so while I appreciate some of your suggestions I will just leave it at that.

Not touching the handbrake or the boot lock either until the retest.

I guess if that 110 euro "investment" doesn't pay off it is time to move on. My mechanic agrees.

Investing any more time and parts into this car is a false economy at this stage.

Will update on 5th July.

wonski · 05-07-2020 11:33pm

Well, improved today, but not enough to pass. Far from it, unfortunately.

And the tester added smoke to the visual defects now, too.

I could see the blue smoke myself today when he revved it, so that's it.

Dirty Nails · 06-07-2020 7:26pm

wonski wrote: »

Well, improved today, but not enough to pass. Far from it, unfortunately.

Your'e not a million miles away from it.
Hc's are unburnt fuel,it's running a bit rich.
In a past post you mentioned " some random misfiring here and there. Nothing out of ordinary"
Random misfire is out of the ordinary,enough to give you those readings.

Diagnostics is much more than reading a fault code,understanding the readings without any codes is the real skill.
I'd give it one more try

wonski · 06-07-2020 10:59pm

Since I cut previous results in half I will have a go again maybe. Retest is 28 euro only anyway.

Will clean the throttle body meself as that's all I can do, see what the garage suggests next, might mention few of the things above.

The only issue is time now. Will book another retest now.

I like your optimism, as these numbers for me are very high still. Never got even close to fail before hence my lack of optimism.

Would be a shame to scrap otherwise good car...

wonski · 06-07-2020 11:15pm

Almost had a heart attack when looked at dates available. Luckily there were some slots available elsewhere. Naas is booked until end of September lol.

Baymax2020 · 06-07-2020 11:16pm

Possibly leaky injector might be worth looking into

Mad_Mike · 06-07-2020 11:26pm

One bad sensor, air leak, air blockage etc could cause figures like that and even higher. I have seen huge figures compared to what you have.
It would be a pity to not figure out what is going on. As @Dirty Nails says, random misfires are totally out of the ordinary and more than likely your problem, but you need to find out why it has random misfires.

What car is this happening with?

wonski · 06-07-2020 11:37pm

Mad_Mike wrote: »

One bad sensor, air leak, air blockage etc could cause figures like that and even higher. I have seen huge figures compared to what you have.
It would be a pity to not figure out what is going on. As @Dirty Nails says, random misfires are totally out of the ordinary and more than likely your problem, but you need to find out why it has random misfires.

What car is this happening with?

2005 Volvo s40 1.8 petrol (not flexi fuel)

Just so we are clear the misfire showed there, but codes were not read prior to this so hard to tell. Will do it again after all was cleared and see if they pop up again.

Booked retest for 17th so plenty of time (or not really).

Emissions fail NCT

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