NCT: Emissions failure

sausagekayak

Hi All,

I've recently put a 05 Mazda 6 (1.8) through the NCT its passed everything except emissions. Any ideas where to start?
Will fuel additives help or are these numbers way off?

Here's the results I got.

Exhaust Emissions:
Engine/Oil temp: 94 °C

Low Idle (700 rpm)
CO 0.38 vol% (Limit 0.5%) Pass
HC 392 ppm Result = N/A

High Idle (2,640 rpm)
Lambda: 1.18 (Pass Range: 0.97 to 1.03) Fail
CO: 0.66 vol% ( Limit 0.3%) Fail
HC 309 ppm (Limit 200 ppm) Fail

Thanks in advance for any advice.

blackbox

The HC and CO are high, but not massively so. This says it is running too rich. The high lambda also says running too rich.

Worst case is that engine is worn and you are burning a lot of oil. You will know this by the need for frequent top-ups and/or blue smoke, especially when starting up. Don't worry too much about small puff of smoke just as it starts.

Other possible reasons for running rich are

restricted air flow - has the air filter been changed in the last year?
• Dirty or faulty MAF.
• Faulty Oxygen sensor (lambda probe).

A worn cat is a possibility, but your readings would probably be worse if that was the case.
After this you are getting into fairly unlikely scenarios...

Pa994

Half a bottle of Dipetane and an Italian tune up

sausagekayak

blackbox wrote: »

The HC and CO are high, but not massively so. This says it is running too rich. The high lambda also says running too rich.

Worst case is that engine is worn and you are burning a lot of oil. You will know this by the need for frequent top-ups and/or blue smoke, especially when starting up. Don't worry too much about small puff of smoke just as it starts.

Other possible reasons for running rich are

restricted air flow - has the air filter been changed in the last year?
• Dirty or faulty MAF.
• Faulty Oxygen sensor (lambda probe).

A worn cat is a possibility, but your readings would probably be worse if that was the case.
After this you are getting into fairly unlikely scenarios...

Thank you very much for the reply. It was running for a week or so with little to no oil while my wife had it, so I have a feeling and really hope the engine is not damaged.

sausagekayak

Pa994 wrote: »

Half a bottle of Dipetane and an Italian tune up

Yes I have read about this, I have the NCT again on Friday, I was thinking I should just use this to get past the NCT then get the car fixed properly.

Would doing this get me passed? Ive read you need to high rev the engine to clear it out?

Steve

Take the lambda sensor out and clean if if you can, seems to be running rich and would bet this is the cause.

Ciano35

A lamda of over 1 suggests it's running lean doesn't it?

Pa994

Do what Steve suggested if at all possible and then run Dipetane for a few days, its 50/50 whether it will work but will have only cost you €35 if it does, if it doesn't will be time to look at other things

sausagekayak

Pa994 wrote: »

Do what Steve suggested if at all possible and then run Dipetane for a few days, its 50/50 whether it will work but will have only cost you €35 if it does, if it doesn't will be time to look at other things

Ok thanks guys, ill give that a shot. Have done some research and looked at a few youtube videos and it does not look too hard to find the o2 sensor and remove it.

Regarding the Diperane, is it just a matter of adding half a bottle and running it for a day or two? Will the car need to be rev'ed up or driven more than to the shops to clear it out?

Mech1

30 miles or so, and drive it like you stole it!

sausagekayak

Mech1 wrote: »

30 miles or so, and drive it like you stole it!

Perfect, will try that, NCT is on Friday so will put it in tonight and should get 30km by then.
Thanks

jca

sausagekayak wrote: »

Perfect, will try that, NCT is on Friday so will put it in tonight and should get 30km by then.
Thanks

Really? And you think adding snake oil and driving the ****e out of an engine that has been run low on oil is going to "fix" it. Any chance you might actually follow some logic like getting it serviced, well, at least change the oil and filter, check the spark plugs and air filter?

sausagekayak

jca wrote: »

Really? And you think adding snake oil and driving the ****e out of an engine that has been run low on oil is going to "fix" it. Any chance you might actually follow some logic like getting it serviced, well, at least change the oil and filter, check the spark plugs and air filter?

No need to be like that!

I will be getting it fixed, its actually up with the mechanic at the moment only his machine for detecting whats wrong is not working.

I have to get the NCT done within a week so might as well try using this "snake oil" and if it fails it fails. Believe me, I understand that this isnt going to fix the issue!!!!!

Thanks for your comment

jca

sausagekayak wrote: »

No need to be like that!

I will be getting it fixed, its actually up with the mechanic at the moment only his machine for detecting whats wrong is not working.

I have to get the NCT done within a week so might as well try using this "snake oil" and if it fails it fails. Believe me, I understand that this isnt going to fix the issue!!!!!

Thanks for your comment

Sorry for being ratty but adding stuff to fuel and Italian tune up suggestions gets on my wick. Could you reschedule the retest until the mechanic gets it fixed?

Special Circumstances

In my completely amateur opinion I also think there is more wrong with this engine than a bottle of dipetane and drive it like you stole it will cure.

The actual emissions showing it running very rich, or on some type of two-stroke mixture, despite lambda showing lean, coupled with having been run low on oil...

I'd love to hear the outcome if you get a chance to come back to us afterwards sausagekayak.

sausagekayak

jca wrote: »

Sorry for being ratty but adding stuff to fuel and Italian tune up suggestions gets on my wick. Could you reschedule the retest until the mechanic gets it fixed?

I would love to reschedule it but they have told me it needs to be retested by Friday otherwise its back to a full test.
Its probably going to fail again and will be a full retest giving me a few weeks to fix it.
I understand where you are coming from, really, this isn't something I would normally do but I don't have time so I though I might as well try the fuel additive. It will be interesting to see if the numbers change.

The car is still scheduled to go back to the mechanic next week either way so I will be getting it fixed.

sausagekayak

Special Circumstances wrote: »

In my completely amateur opinion I also think there is more wrong with this engine than a bottle of dipetane and drive it like you stole it will cure.

The actual emissions showing it running very rich, or on some type of two-stroke mixture, despite lambda showing lean, coupled with having been run low on oil...

I'd love to hear the outcome if you get a chance to come back to us afterwards sausagekayak.

Yea sure, ill keep you guys updated!

jca

sausagekayak wrote: »

Yea sure, ill keep you guys updated!

Please do. Out of curiosity more than anything else. Maybe your mechanic will find something handy, faulty pcv, blocked air filter etc and it turns out to be a cheap fix.

With the high lambda it's probably drawing unmetered air from somewhere like a displaced/leaky vacuum line, a clamp or inlet manifold gasket. You should listen for sucking sounds near the inlet manifold when the engine is idling.

Four Phucs Ache

Hi,

One of my workmates failed nct on emmisions on the same model car you have but 03

New cat was needed....honeycomb inside had broken down.

Pa994

jca wrote: »

Sorry for being ratty but adding stuff to fuel and Italian tune up suggestions gets on my wick. Could you reschedule the retest until the mechanic gets it fixed?

There is no point in putting a new cat or having something like piston rings done if its not necessary? €35 vs €435

jca

Pa994 wrote: »

There is no point in putting a new cat or having something like piston rings done if its not necessary? €35 vs €435

If snake oil fixes it, it doesn't need rings or a cat. A friend of mine had a vintage vauxhall with a clapped out crankshaft, he kept putting in Slick 50 to quieten the knocking big ends..... it worked because a connecting rod punched a hole in the block, it was quiet then.

Four Phucs Ache

Four Phucs Ache wrote: »

Hi,

One of my workmates failed nct on emmisions on the same model car you have but 03

New cat was needed....honeycomb inside had broken down.

The OPs problem is the lambda not at 1.00 though. Nothing points to a broken cat yet. Fitting a new cat to a car with lambda not at 1.00 is total waste of money unless there is actually a hole in the exhaust system at the cat.

Pa994

jca wrote: »

If snake oil fixes it, it doesn't need rings or a cat. A friend of mine had a vintage vauxhall with a clapped out crankshaft, he kept putting in Slick 50 to quieten the knocking big ends..... it worked because a connecting rod punched a hole in the block, it was quiet then.

I've put a car through test and it failed miserably on emissions, put half bottle of dipetane to full tank and drove it about 100 miles went back through test perfectly. Snake oil? If it's been ran with no oil it's f**ked anyway least this will get it through test

blackbox

Ciano35 wrote: »

A lambda of over 1 suggests it's running lean doesn't it?

You are correct Ciano35 - I got this backwards.

kona

A leaky exhaust somewhere would be my bet. I'd be looking aft of the first lambda.

sausagekayak

Pa994 wrote: »

I've put a car through test and it failed miserably on emissions, put half bottle of dipetane to full tank and drove it about 100 miles went back through test perfectly. Snake oil? If it's been ran with no oil it's f**ked anyway least this will get it through test

Whats the ratio of petrol to dipetane I should put in?

sausagekayak

Pa994 wrote: »

I've put a car through test and it failed miserably on emissions, put half bottle of dipetane to full tank and drove it about 100 miles went back through test perfectly. Snake oil? If it's been ran with no oil it's f**ked anyway least this will get it through test

ok just read your comment again correctly, you had a full tank and half a bottle of dipetane :-)

...And Justice

I'm sitting here in the nct centre now, car failed for emissions last time, changed the oxygen sensor and filled the tank with diptaine and petrol, hope it passes, there was some difference in performance after the oxygen sensor was changed out.

...And Justice

Failed on emissions again on high idle CO 0.26% above 0.20% how do I fix this, I've changed out the oxygen sensor and put diptaine in the fuel tank, what else do I need to do.

Originally it failed for HC above 200ppm (220ppm) and CO.36% above 0.20%

Dipetane is a scam. --- You left out the most important number, i.e. the lambda value at high idle. Last time there was a really big excess of oxygen suggesting a leak somewhere.

...And Justice

samih wrote: »

Dipetane is a scam. --- You left out the most important number, i.e. the lambda value at high idle. Last time there was a really big excess of oxygen suggesting a leak somewhere.

Lambda was 0.99, within limits, I'm looking at the CAT now

0.99 is close enough alright although ideally it should be 1.00[0]. Even a small variations in lambda can have big differences in the CO/HC. Typically if the lambda is totally correct even a tired cat is efficient enough. Conversely a brand new cat can bring the emissions marginally under the limit but the car will fail again next time when the new cat ages a bit. If found a good mechanic that properly root caused the issue could save you changing the cat.

Just to give you an idea: My old SAAB 9-5 that was 14 years old at the time of test with a 140k driven cat and oxygen sensor. Everything worked perfectly with a lambda of 1.00 and the resulting CO was 0.01% and HC about 10ppm.

...And Justice

samih wrote: »

0.99 is close enough alright although ideally it should be 1.00[0]. Even a small variations in lambda can have big differences in the CO/HC. Typically if the lambda is totally correct even a tired cat is efficient enough. Conversely a brand new cat can bring the emissions marginally under the limit but the car will fail again next time when the new cat ages a bit. If found a good mechanic that properly root caused the issue could save you changing the cat.

Just to give you an idea: My old SAAB 9-5 that was 14 years old at the time of test with a 140k driven cat and oxygen sensor. Everything worked perfectly with a lambda of 1.00 and the resulting CO was 0.01% and HC about 10ppm.

My HC went from 220 to 15 after diptaine was added, I only failed by 0.6%, on high idle, everything else passed. The only other thing is a faulty/ dirty CAT.

...And Justice

...And Justice wrote: »

samih wrote: »

0.99 is close enough alright although ideally it should be 1.00[0]. Even a small variations in lambda can have big differences in the CO/HC. Typically if the lambda is totally correct even a tired cat is efficient enough. Conversely a brand new cat can bring the emissions marginally under the limit but the car will fail again next time when the new cat ages a bit. If found a good mechanic that properly root caused the issue could save you changing the cat.

Just to give you an idea: My old SAAB 9-5 that was 14 years old at the time of test with a 140k driven cat and oxygen sensor. Everything worked perfectly with a lambda of 1.00 and the resulting CO was 0.01% and HC about 10ppm.

My HC went from 220 to 15 after diptaine was added, I only failed by 0.6%, on high idle, everything else passed. The only other thing is a faulty/ dirty CAT.

I though you changed the Oxy sensor too. Did you check the inlet system for minute leaks? (it could be anything like a loose fitting or deteriorated vacuum hose. If there car is more than a few years old I would change all the vacuum hoses as a matter of cause if they feel soft, brittle or gummy)

...And Justice

samih wrote: »

I though you changed the Oxy sensor too. Did you check the inlet system for minute leaks? (it could be anything like a loose fitting or deteriorated vacuum hose. If there car is more than a few years old I would change all the vacuum hoses as a matter of cause if they feel soft, brittle or gummy)

Tbh I didn't really expect a regular serviced Honda 1.6vtec to fail emissions.

sausagekayak

Ok so I just had my retest and passed.

I did what we discussed here and added a half bottle of Dipetane and filled the tank last Wednesday.
I then drove it very hard up and down some hills to work the engine, did this Thursday and again tonight just before the test.

Ok, so I know there is something wrong with the engine as it didnt pass the emissions test first time, it is booked in for a service next week so we will fix the problem, but atleast I dont have to worry about the NCT now for another year.

Thanks for all the advice guys!


Exhaust Emissions:
Engine/Oil temp: 30 °C

Low Idle (700 rpm)
CO 0.08 vol% (Limit 0.5%) Pass
HC 39 ppm Result = N/A

High Idle (2,770 rpm)
Lambda: 1.01 (Pass Range: 0.97 to 1.03) PASS
CO: 0.05 vol% ( Limit 0.20%) PASS
HC 31 ppm (Limit 200 ppm) PASS

jca

sausagekayak wrote: »

Ok so I just had my retest and passed.

I did what we discussed here and added a half bottle of Dipetane and filled the tank last Wednesday.
I then drove it very hard up and down some hills to work the engine, did this Thursday and again tonight just before the test.

Ok, so I know there is something wrong with the engine as it didnt pass the emissions test first time, it is booked in for a service next week so we will fix the problem, but atleast I dont have to worry about the NCT now for another year.

Thanks for all the advice guys!


Exhaust Emissions:
Engine/Oil temp: 30 °C

Low Idle (700 rpm)
CO 0.08 vol% (Limit 0.5%) Pass
HC 39 ppm Result = N/A

High Idle (2,770 rpm)
Lambda: 1.01 (Pass Range: 0.97 to 1.03) PASS
CO: 0.05 vol% ( Limit 0.20%) PASS
HC 31 ppm (Limit 200 ppm) PASS

Good stuff. Engine oil temp 30°C must be a typo.

Farrellylaughs

Hi guys , I'm new too boards and don't have much knowledge on this but i think I'm on the right thread.

my Volkswagen Jetta 2006 1.6 petrol failed not on the following readings and I'm wondering will i need a new cat converter or lambda sensor or both or is there an easier fix.

Lambda 1.27 not between 0.97 -1.03 (FAIL)
HC 597ppm above 200 PPM (FAIL)

now I'm no mechanic but if its 397 over whats its suppose to be under it must be bad ?

any help would be much appreciated. Thanks guys

damon5

jca wrote: »

Good stuff. Engine oil temp 30°C must be a typo.

Last two times when my car went through the NCT the so called oil temp was 22% and 25% .

Pa994

Farrellylaughs wrote: »

Hi guys , I'm new too boards and don't have much knowledge on this but i think I'm on the right thread.

my Volkswagen Jetta 2006 1.6 petrol failed not on the following readings and I'm wondering will i need a new cat converter or lambda sensor or both or is there an easier fix.

Lambda 1.27 not between 0.97 -1.03 (FAIL)
HC 597ppm above 200 PPM (FAIL)

now I'm no mechanic but if its 397 over whats its suppose to be under it must be bad ?

any help would be much appreciated. Thanks guys

Would consider replacing MAF sensor in air box before anything else, may need codes cleared also

boardsuser1

My 2c worth here lads.

In 2014 I put 2 cars through the nct, both failed on emissions.

I fcuked a full bottle of dipetane into the tank and drove the sh1t out of it before the retest.

Long story short, both cars are now in the scrapyard in the sky.

barneygumble99

Dipetaine is not an emission problem solver. It MAY help when a car is slightly above the limit but in my opinion, the hard driving is of more benefit. Just like with a smoky diesel car, a petrol car also needs a hard drive every so often to clear it out.

I've tested emissions numerous times and generally (9 times out if 10) by looking at the tail pipe insides beforehand you can tell whether a car would pass or fail. When you'd begin the testing (holding the car around 2,700rpm) emissions could be a bit high, and stay at those readings but after giving the car a few sharp hard short revs, up to 5-6,000rpm which a car can handle easily, emission readings come right down. It just needs a clear out. You may even witness this process the next time you visit an nct center.
Also to note that sometimes people think their car passed by the skin of its teeth , 0.19% CO when the limit is 0.20%. Doesn't mean there is an issue with emissions, just means that that was the reading when the machine has reached the testing time limit. For example, our machine takes an initial reading for 30 seconds, if after 10 seconds the reading has remained under the limit , the machine issues a pass but if not, it continues the 30 second countdown and takes whatever reading there is at the 30 second mark.
If it passes it passes, if it fails it continues into another 3.5 minute countdown until it passes (as the cat has gotten red hot) or if it is still failing it follows up with 2 more 30 second countdowns. So for people who think their car is not hot enough after 5 minutes at 2700rpm, as is sometimes blamed on these pages, try putting your hand on the cat then.

damon5

Could you enlighten please,Quote ...I've tested emissions numerous times and generally (9 times out if 10) by looking at the tail pipe insides beforehand you can tell whether a car would pass or fail....end quote.
Also if you have time could you tell me why as the NCT website states that tests will be carried out at normal operating engine temperatures but mine has been done around 23 to 25 degrees for the last few tests.Recently on my last LAMBDA reading it was 0.02 tipping on the boundry of failure with that test result so does the engine temp higher or lower have a differant result when the test is done,cheers.....

barneygumble99

damon5 wrote: »

Could you enlighten please,Quote ...I've tested emissions numerous times and generally (9 times out if 10) by looking at the tail pipe insides beforehand you can tell whether a car would pass or fail....end quote.
Also if you have time could you tell me why as the NCT website states that tests will be carried out at normal operating engine temperatures but mine has been done around 23 to 25 degrees for the last few tests.Recently on my last LAMBDA reading it was 0.02 tipping on the boundry of failure with that test result so does the engine temp higher or lower have a differant result when the test is done,cheers.....

As regards petrol , If the insides of the tailpipe are carbon free it generally indicates a healthy engine as regards emissions, and vice versa if it is heavily coated in carbon. Like I said this is only a general indicator.

Well if the car is passing the test there is no need to take a temperature reading so 23 or 25 may be just be a default reading. Temperature reading is only required when a car is failing. A car would reach 23 degrees within a minute of starting so it is obviously a lot hotter by the time it is being tested. In most cases though, the hotter the car, the more efficiently the car runs which is why it goes through such a long cycle if it is failing.

damon5

barneygumble99 wrote: »

As regards petrol , If the insides of the tailpipe are carbon free it generally indicates a healthy engine as regards emissions, and vice versa if it is heavily coated in carbon. Like I said this is only a general indicator.

Well if the car is passing the test there is no need to take a temperature reading so 23 or 25 may be just be a default reading. Temperature reading is only required when a car is failing. A car would reach 23 degrees within a minute of starting so it is obviously a lot hotter by the time it is being tested. In most cases though, the hotter the car, the more efficiently the car runs which is why it goes through such a long cycle if it is failing.

Thanks for your informative replies that are literally from the horses mouth so to speak.With so much misinformation on the web it can be very hard to find a correct answer to a problem.