NCT high CO result

Renno123

hi guys,
does anyone have any opinions on whats going on with my 03 Focus before i can get it to a garage.
car failed NCT on emissions.

engine oil temp : 99oC Isnt this usually 15oC?

Low idle: 710 rpm
CO 0.79 vol% FAIL
HC 422ppm N/A

High Idle 2820 rpm
Lambda 1.02 PASS
CO 0.55vol% FAIL
HC 118ppm PASS

Anyone have any idea what the issue is?
thanks

Leonard Hofstadter

Well it's running a bit lean so that won't help matters, although getting it back to 1 is unlikely to improve it enough to make it pass the CO readings.

Is it burning oil? Is the engine malfunction light on?

Renno123

captainspeed wrote: »

Well it's running a bit lean so that won't help matters, although getting it back to 1 is unlikely to improve it enough to make it pass the CO readings.

Is it burning oil? Is the engine malfunction light on?

12 months ago the lamba was reading 1.02 as well, so no change there.
car isnt burning oil, not in any way too noticeable, ive topped it up the odd time. maybe 2 ltrs over 14 months.
no engine lights are on.

pablo128

Renno123 wrote: »

12 months ago the lamba was reading 1.02 as well, so no change there.
car isnt burning oil, not in any way too noticeable, ive topped it up the odd time. maybe 2 ltrs over 14 months.
no engine lights are on.

The lambda constantly fluctuates between 0.97 and 1.03 so any figure between those two is a pass.

When was the car last serviced?

Renno123

pablo128 wrote: »

The lambda constantly fluctuates between 0.97 and 1.03 so any figure between those two is a pass.

When was the car last serviced?

car had a full service 6 weeks ago

gerryo

Renno123 wrote: »

hi guys,
does anyone have any opinions on whats going on with my 03 Focus before i can get it to a garage.
car failed NCT on emissions.

engine oil temp : 99oC Isnt this usually 15oC?

Low idle: 710 rpm
CO 0.79 vol% FAIL
HC 422ppm N/A

High Idle 2820 rpm
Lambda 1.02 PASS
CO 0.55vol% FAIL
HC 118ppm PASS

Anyone have any idea what the issue is?
thanks

I had a problem like that with a Vectra, just over the limit.
Tried everything to get it down, ended up getting a new lambda + catalytic converter.

Is you catalytic converter Ok, does it rattle when going over bumps (hard to check I guess).
If you are burning oil, the catalytic converter lifespan is reduced. If you have never changed it, it's probably not working well by now.

Renno123

gerryo wrote: »

I had a problem like that with a Vectra, just over the limit.
Tried everything to get it down, ended up getting a new lambda + catalytic converter.

Is you catalytic converter Ok, does it rattle when going over bumps (hard to check I guess).
If you are burning oil, the catalytic converter lifespan is reduced. If you have never changed it, it's probably not working well by now.

I don't know about any noise,
I'll get a new one priced

Leonard Hofstadter

If the cat isn't working the malfunction light should have come on, there is a DTC for when the cat isn't working as well as it should be.

I would be slow enough to replace a cat without proof that it's at fault. Now it may well be the case here if there's no oil burning and it's otherwise running fine but I'd be trying to rule out other causes first (as the other possible causes won't be as expensive to fix). If the underlying problem isn't fixed then the cat will need to be replaced again, cats can tolerate a certain amount of the incorrect fuel/air mix and high CO/HC emissions (if they didn't, you could never have a cold engine as they run richer than a warmed up engine) but it is a finite amount of time.

As it's just had a service we can rule out old oil being a possible cause.

Has the O2 (lambda) sensor ever been replaced? When was the last time the spark plugs were changed? What about the air bellows? Does the car feel like it's down on power?

Have you taken it for a good motorway blast any time recently? If it hadn't had a good hard drive then there could be carbon buildup and that would cause the high emissions (although the lean reading suggests this is unlikely).

If it hasn't had a high speed run in quite a while you could try a good motorway blast at high revs (4th gear at the full 120 km/h for at least half an hour) with a bottle of injector cleaner stuck into the fuel tank, it mightn't make a difference but again it will rule out too much gentle driving as a possible cause (all cars need a good thrashing every now and again to keep everything running sweetly and to keep the emissions in spec).

By the way OP if the car was tested at 99C then that means the engine was fully warmed up (which should have helped rather than hindered you passing the NCT).

Waterson

Your engine is running rich. This may be because of a perceived lean condition in the exhaust emissions. Fuel trim data with a scantool will tell you for sure. Avoid any garage who immediately tell you to replace lambda sensor or CAT without checking how the engine itself is running. These clowns are everywhere unfortunately.

rex-x

The engine is running slightly lean, not rich. Op your Hc levels are quite high which is indicative of an engine not running at its best. The high Co reading suggests poor cat performance but it is marginal so if the car hasnt been serviced in a while then it would be a good idea.
It is likely you have an engine that's not particularly well cared if with a tired cat but get it hot enough and it may pull back in line for the test

Renno123

rex-x wrote: »

The engine is running slightly lean, not rich. Op your Hc levels are quite high which is indicative of an engine not running at its best. The high Co reading suggests poor cat performance but it is marginal so if the car hasnt been serviced in a while then it would be a good idea.
It is likely you have an engine that's not particularly well cared if with a tired cat but get it hot enough and it may pull back in line for the test

Thanks, the car is good condition for its age besides this problem. 03 and 90,000miles. Full service history every 8,000-10000 miles.
If it sounds like the engine is getting tired then I'll get a new car.
What tests can someone do to find out what is wrong?

Waterson

Let's look at the test results. You have a lambda greater than 1. This shows a lean condition in the exhaust emissions. Suppose that this leak is a hole in the exhaust/leaky manifold gasket on the engine side of the pre CAT lambda sensor. The sensor will register this excess of air and increase the amount of fuel injected to compensate to keep the air/fuel ratio in spec. Your engine is now running rich. This would be evident by excessive hydrocarbons (HCs) and carbon monoxide (CO).
Suppose your engine were running lean, i.e. a vacuum leak or low fuel pressure. Your lambda reading would be within spec or slightly on the rich side as not as much air would be passing through to the exhaust. The computer would adjust the fuel trims positively (increase injector opening time) to compensate. Also you would most likely have a emissions failure at idle speed but pass at high idle where vacuum leaks won't affect the running of engine as much.
This is all speculation and can't be affirmed without fuel trim data which any generic scantool can give you. The clue here is the lambda reading.

Renno123

so my first port of call would be top get an emissions & diagnostic test?

Waterson

Absolutely. Have your mechanic check fuel trims and report back the results we can advise you further.

Renno123

so i had the car booked in for a diagnostic and emission test. 2 hours waiting and got told its probably the CAT, and they want to fit a new one and see. i was not impressed as they didnt actually do any diagnostic test.
What should the diagnostic test results show?
should i receive paperwork showing this?

Waterson

You need to find out how your engine is running in terms of fuelling. Short and long term fuel trims. It may be that the CAT is faulty, but what if the underlying reason for that is an overfuelling issue? You might get a pass this time won't get too long out of the new part. They should be able to show you a screenshot of their diagnostic procedure or at least an look atbrh3 oxygen sensor waveforms pre and post CAT. If they look the same it may be that the CAT is faulty.

Renno123

Waterson wrote: »

You need to find out how your engine id running in terms of fuelling. Hurt and long term fuel trims. It may be that the CAT is faulty, but what if the underlying reason for that is an overfuelling issue? You might get a pass this time won't get too long out of the new part. They should be able to show you a screenshot of their diagnostic procedure or at least an look atbrh3 oxygen sensor waveforms pre and post CAT. If they look the same it may be that the CAT is faulty.

booked in for sat morning in the main dealer so ill post results

pablo128

I'll just add that we supply exhaust parts in work, and Focus cats are a big seller. I wouldn't be too quick to dismiss it as the problem.

I don't think they're mad money either.

Waterson

Definitely not dismissing the CAT, but I would want to see proof before handing over €300 or so...but i have seen many many instances of CATs and lambda sensors being replaced unnecessarily at the customers expense when the actual faults were as insubstantial as perished vacuum hoses, plugged fuel filters and bogey MAP sensors.

Renno123

got a few quotes for a cat replacement and its coming in at €230-€250 parts & labour which is fine.

the focus has a useful feature where u can run a self diagnostic test. mine came up DTC=NONE.
i still have it booked in for a diagnostic with the main dealer, but it would seem that no faults are detected.
would this suggest that the cat is in fact at fault?