NCT Fail - CO Emissions

AstraOwner

Recent NCT failure on an Astra G due to high CO emissions. Readings from the test are as follows:


Engine/Oil Temperature 83C

Low Idle (820 rpm)

CO 0.59 vol% - above 0.50% fail FAIL/REFUSAL
HC 235ppm - N/A

High Idle (2,940 rpm)

Lambda: 1.03 - not between .97 and 1.03 fail PASS
CO 0.72 VOL% - above 0.30% fail FAIL/REFUSAL
HC 178ppm - above 200 ppm fail PASS


I didn't drive the **** out of it before the test and used no additives as I didn't think they would be necessary. Though the tester sustained it at high idle for a long time during the test.


I fitted a new catalytic converter to the car just 7 weeks ago which is why I'm a bit surprised with the CO readings now. The old cat was at least 7 or 8 years old and had disintegrated. The new cat was a React catalytic converter, as seen here.

The car has never burnt any noticeable oil and recently had an oil and filter change. (There is probably a bit too much oil in at the moment which will be rectified today).


Any expert suggestions/opinions on what the issue is here? I'll get it to a garage next week if needs be for a diagnosis.

jimgoose

According to that Lambda reading it's running quite lean, but the HC and CO levels would appear to contradict that. I'd suspect the Lambda sensor itself. Get it scanned for OBD codes, assuming it's post-2001.

AstraOwner

Pre 2001
Thanks jimgoose.

AstraOwner

I know the EGR can often be an issue on these (although it hasn't been on this car to date). Would a faulty EGR lead to the above readings?
The car was a bit jumpy in the past but a new coil pack sorted that. I have noticed it become a bit jumpy again recently.

jimgoose

AstraOwner wrote: »

I know the EGR can often be an issue on these (although it hasn't been on this car to date). Would a faulty EGR lead to the above readings?

I doubt it - EGR problems tend to affect the NOx readings, and if it's stuck closed older cars usually burn better. Check for air-leaks around the intake as well, as you're at it. You never know.

AstraOwner

jimgoose wrote: »

Normally I'd say go for it, but that Lambda reading would have me annoyed.

Thanks again Jim. (Sorry crossed accounts with my last post. My laptop is giving me trouble too) :mad:

jimgoose

AstraOwner wrote: »

Thanks again Jim. (Sorry crossed accounts with my last post. My laptop is giving me trouble too) :mad:

Oh, right. I thought someone mis-fired!

AstraOwner

The backbox on the car is in bad aul nick and will need replacing soon. Although there are no leaks/noise and the NCT never mentioned it.
But I wonder if it might be leaking slightly to cause the 1.03 Lambda reading?

Greenmachine

My one piece of advice if you are ordering the lambda yourself is to go with bosch instead of a spurious brand.

jimgoose

AstraOwner wrote: »

The backbox on the car is in bad aul nick and will need replacing soon. Although there are no leaks/noise and the NCT never mentioned it.
But I wonder if it might be leaking slightly to cause the 1.03 Lambda reading?

Back-box? Doubt it.

AstraOwner

Ah. I just had a quick look and the exhaust is leaking at the front pipe to manifold gasket. (The lambda sensor is just above/before this)

What would that explain? Slightly high Lambda reading?

jimgoose

AstraOwner wrote: »

Ah. I just had a quick look and the exhaust is leaking at the front pipe to manifold gasket. The lambda sensor is just above this.

What would that explain? Slightly high Lambda reading?

A-ha! The Lambda is detecting excess oxygen because of this unmetered air that never entered the engine. It is then telling the ECU to squirt more fuel to burn up the oxygen that isn't in fact there, thus blowing HC and CO. Fix leak, sorted.

wonski

Failed emissions two times due to a leaking exhaust and on each occasion lambda readings were to high. The other values were well within limits.
It was a middle box if it makes any difference.

AstraOwner

jimgoose wrote: »

A-ha! The Lambda is detecting excess oxygen because of this unmetered air that never entered the engine. It is then telling the ECU to squirt more fuel to burn up the oxygen that isn't in fact there, thus blowing HC and CO. Fix leak, sorted.

The leak is definitely a couple of inches after the sensor in the system. Would the sensor still pick this up?
The leak is blowing quite a bit. Very easy to feel with fingers.

jimgoose

AstraOwner wrote: »

The leak is definitely a couple of inches after the sensor in the system. Would the sensor still pick this up?
The leak is blowing quite a bit. Very easy to feel with fingers.

Quite possible, I should say.

AstraOwner

Well if that's the fault I'll be a very happy chappy! Thanks Jim

AstraOwner

Haven't had any chance to go near this yet. But I had it on a spin across the country today. I really don't think the car is using any more petrol than usual. I'm almost sure of it. Hope that doesn't point to a cat issue.

Isopon

I have 1 word for you. Terraclean. Google it. It will sort it out for you

SJPK

Would a leak from the exhaust manifold , worn gasket, effect emmissions?

jimgoose

SJPK wrote: »

Would a leak from the exhaust manifold , worn gasket, effect emmissions?

Most likely, yes.

jca

SJPK wrote: »

Would a leak from the exhaust manifold , worn gasket, effect emmissions?

Of course it will. Fix the obvious before throwing cans of crap into the fuel.

jimgoose

jca wrote: »

Of course it will. Fix the obvious before throwing cans of crap into the fuel.

Some people don't make the link between a wee hole in a piece of plumbing and something terrifyingly technical like emissions problems until it's explained to them.

AstraOwner

FIRST TEST


Engine/Oil Temperature 83C

Low Idle (820 rpm)

CO 0.59 vol% - above 0.50% fail FAIL/REFUSAL
HC 235ppm - N/A

High Idle (2,940 rpm)

Lambda: 1.03 - not between .97 and 1.03 fail PASS
CO 0.72 VOL% - above 0.30% fail FAIL/REFUSAL
HC 178ppm - above 200 ppm fail PASS



RETEST


Engine/Oil Temperature 104C

Low Idle (810 rpm)

CO 0.31 vol% - above 0.50% fail PASS
HC 108ppm - N/A

High Idle (2,960 rpm)

Lambda: 1.01 - not between .97 and 1.03 fail PASS
CO 0.43 VOL% - above 0.30% fail FAIL/REFUSAL
HC 92ppm - above 200 ppm fail PASS



IN BETWEEN

Repaired front pipe to manifold gasket.
Gave the EGR a bit of a clean.
Used Dipetane.
Gave the car a good drive before bringing it in this time.

A lot better but not good enough. The CO at low idle has almost halved and passed it well. The CO at high idle dropped a lot. The tester gave it every chance and said he had it/almost had it under .30% for a second but couldn't keep it there.
HC figures dropped a lot and the Lambda figure has improved.


I'll have to get it checked over to see where the issue is, but any ideas?
(Cat is only 7 or 8 weeks old,
No problems with losing oil,
oil change recently)

jca

AstraOwner wrote: »

FIRST TEST


Engine/Oil Temperature 83C

Low Idle (820 rpm)

CO 0.59 vol% - above 0.50% fail FAIL/REFUSAL
HC 235ppm - N/A

High Idle (2,940 rpm)

Lambda: 1.03 - not between .97 and 1.03 fail PASS
CO 0.72 VOL% - above 0.30% fail FAIL/REFUSAL
HC 178ppm - above 200 ppm fail PASS



RETEST


Engine/Oil Temperature 104C

Low Idle (810 rpm)

CO 0.31 vol% - above 0.50% fail PASS
HC 108ppm - N/A

High Idle (2,960 rpm)

Lambda: 1.01 - not between .97 and 1.03 fail PASS
CO 0.43 VOL% - above 0.30% fail FAIL/REFUSAL
HC 92ppm - above 200 ppm fail PASS



IN BETWEEN

Repaired front pipe to manifold gasket.
Gave the EGR a bit of a clean.
Used Dipetane.
Gave the car a good drive before bringing it in this time.

A lot better but not good enough. The CO at low idle has almost halved and passed it well. The CO at high idle dropped a lot. The tester gave it every chance and said he had it/almost had it under .30% for a second but couldn't keep it there.
HC figures dropped a lot and the Lambda figure has improved.


I'll have to get it checked over to see where the issue is, but any ideas?
(Cat is only 7 or 8 weeks old,
No problems with losing oil,
oil change recently)

Feck that's so bloody close. Did you lower the slightly high oil level? What's the air filter like?

AstraOwner

jca wrote: »

Feck that's so bloody close. Did you lower the slightly high oil level? What's the air filter like?

Bloody close alright jca.

Yes I forgot to mention that I lowered the level of the oil.

The air filter looked in good shape. It was renewed last year sometime. I banged a bit of dust off it is all.
I hear differing opinions about going through the NCT with no air filter. It's not something I'd love to be doing but I wonder if it would get me under the limit?

vince

Sounds identical to my 98 megane last month I gave up in the end so close to passing. Fine car now parked up. In my case I had the air filter out on all my imission tests at the local garage didnt make much differance. Good luck whit it such a wind up when you see smokey old trucks pass you by.

V.W.L 11

Sadly the oul Bora failed her nct this morning,just the emissions nothing else,the car is perfect that aside,tbh I didn't even suspect it had that issue,the issues I did suspect never happened then :rolleyes: it failed as follows:

High Idle;

CO 1.92% anything above 0.30% is a failure

HC757ppm,anything above 200ppm is a failure

the lambda itself was actually within the limits,it came in at 1.01,the tolerance limits are 0.97 and 1.03

is it the catalytic converter that is fcuked???

AstraOwner

I think you've got more than a cat issue.


New cat sorted me out in the end.

V.W.L 11

AstraOwner wrote: »

I think you've got more than a cat issue.


New cat sorted me out in the end.

any idea's what it could be OP???I hope to god its only the cat.

AstraOwner

Perhaps it is. I can't claim to be any expert on it. I think the figures are too high though for just a cat problem.
It might be a case that a cat will sort it for the test but the problem will remain (and f*** up the new cat).
Post the other half of the emissions results as well and it might make it easier to diagnose.

Kopparberg Strawberry and Lime

V.W.L 11 wrote: »

any idea's what it could be OP???I hope to god its only the cat.

Glad Astra owner is sorted !

As for the bora... is it a 1.4 engine around 1998 - 2003 ?

V.W.L 11

AstraOwner wrote: »

Perhaps it is. I can't claim to be any expert on it. I think the figures are too high though for just a cat problem.
It might be a case that a cat will sort it for the test but the problem will remain (and f*** up the new cat).
Post the other half of the emissions results as well and it might make it easier to diagnose.

Low idle
(770rpm)

CO 0.23,anything above 0.50% is a failure
HC 335

there is no limit for the HC on low idle,under the heading of results it just says N/A.


The low idle is comfortably within the limits,its just the high idle that failed,that aside the car is 110%,for a 2000 with 145k miles on it its actually in very good condition.

V.W.L 11

Kopparberg Strawberry and Lime wrote: »

Glad Astra owner is sorted !

As for the bora... is it a 1.4 engine around 1998 - 2003 ?

that's the engine OP,she's the 16V,she's a 2000 reg.

Kopparberg Strawberry and Lime

V.W.L 11 wrote: »

that's the engine OP,she's the 16V,she's a 2000 reg.

O rings, valve stem oil seals gone... needs an engine rebuild

V.W.L 11

Kopparberg Strawberry and Lime wrote: »

O rings, valve stem oil seals gone... needs an engine rebuild

costly job so???

Kopparberg Strawberry and Lime

V.W.L 11 wrote: »

costly job so???

Indeed... around the 700 mark for it all

V.W.L 11

Kopparberg Strawberry and Lime wrote: »

Indeed... around the 700 mark for it all

i'll take it to the mechanic I suppose,let him have a look first hand

V.W.L 11

went to a VW specialist dismantler,the guy is at it 20 years,he said that it could be a faulty lamda reading,could need a service also,the car is NOT spurting out smoke no differently to any other car,the oil hasn't been changed in almost a year,nor have any other serviceable components for that matter,so I am hoping this may sort the issue.

P.S the engine temperature was 81 degrees Celsius,i think I may need to drive the sh1t out of it also to sort the problem.

AstraOwner

Driving the **** out of it and even Dipetane will help, but it still won't be near passing. Make sure there are no exhaust leaks.

Getting the service goes without saying.

If it is indeed the lambda and you're getting somebody to do it it'll pay to get somebody who has the equipment to check the emissions once they are finished. imo

I presume that whatever the problem, the cat is f**ked too.

V.W.L 11

AstraOwner wrote: »

Driving the **** out of it and even Dipetane will help, but it still won't be near passing. Make sure there are no exhaust leaks.

Getting the service goes without saying.

If it is indeed the lambda and you're getting somebody to do it it'll pay to get somebody who has the equipment to check the emissions once they are finished. imo

I presume that whatever the problem, the cat is f**ked too.

dodgy gasket between the exhaust and cat maybe?i had that with a subaru many years ago,there is no blue smoke out the back of the car to suggest is it burning oil,its going to the mechanic on tuesday anyway

AstraOwner

Checking for holes would be a standard check, but you have more going on.
But again, I wouldn't be best qualified to give advice here.

Let us know how you get on anyway.

V.W.L 11

AstraOwner wrote: »

Checking for holes would be a standard check, but you have more going on.
But again, I wouldn't be best qualified to give advice here.

Let us know how you get on anyway.

thanks astraowner i was told it would be puffing out blue smoke if the seals were gone,yer man never mentioned it in the test centre,maybe the cat. is full of sh1t and needs a good clean out,tuesday should tell

V.W.L 11

now i'm baffled,i revved the car to exactly the same (or slightly more) revs the nct inspector did this morning,and for the life of me I cannot see anything out of the ordinary with it,i had a seat cordoba of the same year once and the car is acting no differently,have I been had?the only way I could imagine getting the readings that appear on the sheet is by red lining it (which I didn't do) confused.com

jca

V.W.L 11 wrote: »

now i'm baffled,i revved the car to exactly the same (or slightly more) revs the nct inspector did this morning,and for the life of me I cannot see anything out of the ordinary with it,i had a seat cordoba of the same year once and the car is acting no differently,have I been had?the only way I could imagine getting the readings that appear on the sheet is by red lining it (which I didn't do) confused.com

What are you expecting to see? CO is an invisible odorless gas.

V.W.L 11

jca wrote: »

What are you expecting to see? CO is an invisible odorless gas.

point taken!!!from what I can see from other boardsies who had similar issues the cat could well do with a clean out or a change,it was only caught at high idle