NCT - Failed on Emissions

Bansko

Hi there,

I've recently put a 00 Corolla (1.4VVTI) through the NCT its passed everything except emissions. Any ideas where to start with repairs?

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.

sean1141

try some fuel additive (can be got in most motor factors just tell them what you want it for) add it and drive the car for a few days. add a second top-up before you go back for the retest. when you are going go a few mins earlier and drive the car in third gear keeping a high rev on it but not too high lol

Does the engine burn loads of oil?

shamwari

looks like oil burning, plus the lambda being off too suggests there might be a hole in the exhaust.

mullingar

Your lambda reading is waaayyyy off.

Get your lambda sensor(s) checked. This can be a DIY with a mulitmeter.

+1 on possibly burning oil too

shamwari

Lambda being way off is caused by holes in the exhaust, not the lambda / O2 sensors!

Bansko

Yes burns a bit of oil alright... whats the next step??

(Had exhaust checked at quick fit before NCT and they gave it thumbs up)

shamwari

Bansko wrote: »

Yes burns a bit of oil alright... whats the next step??

(Had exhaust checked at quick fit before NCT and they gave it thumbs up)

Strange, any time I've seen lambda off was an exhaust issue of some sort. Is your car a high miler??

BrianD3

shamwari wrote: »

Strange, any time I've seen lambda off was an exhaust issue of some sort. Is your car a high miler??

If lambda is >1.03 and everything else passes, it is very likely to be due to a hole in the exhaust. However if CO and/or HC are failing as well then various things could be happening.

Bansko

Thanks Guys, I'll check the Lambda Sensor first and report back..

(How does the NCT measure the lambda by the way ?)

shamwari

Hopefully this will help (quote from McNamara's website) which apply to Petrol engines during NCT. I emphasised some of it in bold

There are three different readings taken when your car is tested at the National car test centre.

Carbon Monoxide (CO)
Carbon monoxide is a colourless, odourless, poisonous gas formed by incomplete combustion of petrol. This gas is emitted directly from the vehicle exhaust pipe. Incomplete combustion most commonly occurs at low air to fuel ratios in the engine. This means there is not enough air in the combustion chamber to burn all the fuel entering it.

Hydrocarbons (H.C)
Hydrocarbon emissions result when fuel molecules in the engine do not burn or burn only partially. Hydrocarbons react in the presence of nitrogen oxides and sunlight to form ground-level ozone, a major component of smog. Ozone irritates the eyes, damages the lungs, and aggravates respiratory problems. It is our most widespread and intractable urban air pollution problem. A number of exhaust hydrocarbons are also toxic, with the potential to cause cancer.

Lambda
The lambda reading is not a gas but a ratio of air to fuel in the exhaust. An ideal lambda reading is 1. This means that all the fuel entering the combustion chamber is being burnt. In reality, cars are usually minutely rich or lean or varying between the two. This is the reason a variation of 0.03 is allowed on either side of the ideal ration of 1:1. A common misconception is that if your car fails the NCT on Lambda it means your oxygen (lambda) sensor in the exhaust is faulty. This may well be the case but it could also be the sign of an exhaust leak or another problem in the engine.

Bansko

shamwari wrote: »

Hopefully this will help (quote from McNamara's website) which apply to Petrol engines during NCT. I emphasised some of it in bold

There are three different readings taken when your car is tested at the National car test centre.

Carbon Monoxide (CO)
Carbon monoxide is a colourless, odourless, poisonous gas formed by incomplete combustion of petrol. This gas is emitted directly from the vehicle exhaust pipe. Incomplete combustion most commonly occurs at low air to fuel ratios in the engine. This means there is not enough air in the combustion chamber to burn all the fuel entering it.

Hydrocarbons (H.C)
Hydrocarbon emissions result when fuel molecules in the engine do not burn or burn only partially. Hydrocarbons react in the presence of nitrogen oxides and sunlight to form ground-level ozone, a major component of smog. Ozone irritates the eyes, damages the lungs, and aggravates respiratory problems. It is our most widespread and intractable urban air pollution problem. A number of exhaust hydrocarbons are also toxic, with the potential to cause cancer.

Lambda
The lambda reading is not a gas but a ratio of air to fuel in the exhaust. An ideal lambda reading is 1. This means that all the fuel entering the combustion chamber is being burnt. In reality, cars are usually minutely rich or lean or varying between the two. This is the reason a variation of 0.03 is allowed on either side of the ideal ration of 1:1. A common misconception is that if your car fails the NCT on Lambda it means your oxygen (lambda) sensor in the exhaust is faulty. This may well be the case but it could also be the sign of an exhaust leak or another problem in the engine.

Thanks Shamwari...

So If I understand this right..

Hi CO = Unburned fuel in Exhaust

Hi HC = Unburned Fuel in Exaust

Hi Lambda = High Ratio of Air/Fuel in Exhaust (Air = 1.18 =x Fuel ?) so this could mean extra air is getting into the exhaust somewhere making the ECU think the car is running lean and then it pumps more fuel in?? hence the high HC and CO??? or maybe no leak and faulty lambda sensor causing same symptoms??

( How about the burning oil, could that mask complicate readings?)

Plug

Bansko wrote: »

Thanks Shamwari...

So If I understand this right..

Hi CO = Unburned fuel in Exhaust

Hi HC = Unburned Fuel in Exaust

Hi Lambda = High Ratio of Air/Fuel in Exhaust (Air = 1.18 =x Fuel ?) so this could mean extra air is getting into the exhaust somewhere making the ECU think the car is running lean and then it pumps more fuel in?? hence the high HC and CO??? or maybe no leak and faulty lambda sensor causing same symptoms??

( How about the burning oil, could that mask complicate readings?)

Start your engine and stick a rag in the exhaust pipe and listen for the exhaust blowing somewhere.

shamwari

Bansko wrote: »

Thanks Shamwari...

So If I understand this right..

Hi CO = Unburned fuel in Exhaust

Hi HC = Unburned Fuel in Exaust

Hi Lambda = High Ratio of Air/Fuel in Exhaust (Air = 1.18 =x Fuel ?) so this could mean extra air is getting into the exhaust somewhere making the ECU think the car is running lean and then it pumps more fuel in?? hence the high HC and CO??? or maybe no leak and faulty lambda sensor causing same symptoms??

( How about the burning oil, could that mask complicate readings?)

What can happen is:

Engine burns oil = Hi HC

Oil deposits screw up the O2 sensor and cause Hi CO. Hi CO can also be caused by a duff cat. Your cat seems to be ok at idle though. Hi idle its struggling.

How much oil is your car burning (how often is it topped up and by how much?) What mileage is it? Are the spark plugs ok, or are they sooty and black? Is the engine reaching correct temperature? Is the fuel consumption particularly heavy?

if you car is going through lots of oil then this is gonna be a big problem to get this thru the test, and those VVTi's are known for burning oil when the mileage goes up.

Bansko

shamwari wrote: »

What can happen is:

Engine burns oil = Hi HC

Oil deposits screw up the O2 sensor and cause Hi CO. Hi CO can also be caused by a duff cat. Your cat seems to be ok at idle though. Hi idle its struggling.

How much oil is your car burning (how often is it topped up and by how much?) What mileage is it? Are the spark plugs ok, or are they sooty and black? Is the engine reaching correct temperature? Is the fuel consumption particularly heavy?

if you car is going through lots of oil then this is gonna be a big problem to get this thru the test, and those VVTi's are known for burning oil when the mileage goes up.

Thanks for some great advice..

The Car hasn't been used much since I got it so its hard to comment on fuel/oil consumption (Although Trip comp is saying about 33.8MPG) Previous owner mentioned he changed the CAT trying to get it to pass emissions, but I don't know how long he's been driving on the new CAT.

Mileage = 97K.. I'll check the following next time I get some daylight time with the car.. prob next weekend.

1. Rag in Exhaust - Check for Air leaks.

2. Check Lambda Sensor ( is o2 and lambda the same?)

3. Check plugs ( I'll change them and Oil/filter while I'm at it)

Is there any way to monitor any of the 3 outputs to see if anything improves before putting it back though the NCT? (I'd consider getting a scan tool if that would do the job - not sure what readings you would get on a 00 corolla)

David09

Is there any visible bluish smoke when the engine is revved up or after it's been running at idle for a while?

shamwari

Bansko wrote: »

Thanks for some great advice..

The Car hasn't been used much since I got it so its hard to comment on fuel/oil consumption (Although Trip comp is saying about 33.8MPG) Previous owner mentioned he changed the CAT trying to get it to pass emissions, but I don't know how long he's been driving on the new CAT.

Mileage = 97K.. I'll check the following next time I get some daylight time with the car.. prob next weekend.

1. Rag in Exhaust - Check for Air leaks.

2. Check Lambda Sensor ( is o2 and lambda the same?)

3. Check plugs ( I'll change them and Oil/filter while I'm at it)

Is there any way to monitor any of the 3 outputs to see if anything improves before putting it back though the NCT? (I'd consider getting a scan tool if that would do the job - not sure what readings you would get on a 00 corolla)

to answer 2 above, O2 / Lambda sensor are the same. A good service will help too, and an oil flush might help if it's burning oil. The three outputs (CO / HC / Lambda) cannot be measured without a gas analyser. A scan tool will at best only give you engine live data and fault codes (incl O2 sensor switching), It won't give you the three emissions readings that are failing the test. For the cost of the scantool, you might be better off bringing the car somewhere that has gas analysers and scantools, and let them tell you what they think.

I also meant to ask you, the car doesn't have a misfire does it? Apart from burning oil, the only other thing that would cause readings like that would be a significant misfire....:eek:

Bansko

shamwari wrote: »

to answer 2 above, O2 / Lambda sensor are the same. A good service will help too, and an oil flush might help if it's burning oil. The three outputs (CO / HC / Lambda) cannot be measured without a gas analyser. A scan tool will at best only give you engine live data and fault codes (incl O2 sensor switching), It won't give you the three emissions readings that are failing the test. For the cost of the scantool, you might be better off bringing the car somewhere that has gas analysers and scantools, and let them tell you what they think.

I also meant to ask you, the car doesn't have a misfire does it? Apart from burning oil, the only other thing that would cause readings like that would be a significant misfire....:eek:

Drives very smooth.. haven't noticed a misfire.

Saw this on Youtube (http://www.youtube.com/watch?v=Y4EAyYI67Cw) and was thinking if the corolla had a fuel trim PID that I might be able to get an indication of emissions from the reading.. but I'm guessing monitoring the Lambda sensor on an Oscilloscope will give similar information.

Can you recommend a good garage for fault finding emissions problems?

shamwari

Bansko wrote: »

Drives very smooth.. haven't noticed a misfire.

Saw this on Youtube (http://www.youtube.com/watch?v=Y4EAyYI67Cw) and was thinking if the corolla had a fuel trim PID that I might be able to get an indication of emissions from the reading.. but I'm guessing monitoring the Lambda sensor on an Oscilloscope will give similar information.

Can you recommend a good garage for fault finding emissions problems?

You can check the O2 sensor switching by using a scope or a DMM with a fast rise time. Again this will not show you what the emissions are like, which are measured downstream from the cat. It is highly highly unlikely that this is anything to do with fuel trim either. Short term fuel trims change with driving characteristics, whilst long term trims are compensation for engine wear and the likes, and to keep emissions within tolerances. Where are you based by the way?

Bansko

shamwari wrote: »

You can check the O2 sensor switching by using a scope or a DMM with a fast rise time. Again this will not show you what the emissions are like, which are measured downstream from the cat. It is highly highly unlikely that this is anything to do with fuel trim either. Short term fuel trims change with driving characteristics, whilst long term trims are compensation for engine wear and the likes, and to keep emissions within tolerances. Where are you based by the way?

I'm living in Tallaght, although I'm in Rush some weekend's Do you have garage/gas analyser? would you be interested in taking a look at it?

shamwari

I don't have a gas analyser, but a friend of mine has a garage in the city centre, and he deffo has one alright. I'll be talking to him later about another job and I'll mention it to him, and ask what he can do it for (reasonably of course!!)

AzureAuto

A higher lambda reading indicates an excess of air in the exhaust. Now assuming Quickfit found no leaks, this air may be leaching into system from a variety of places, i.e. split vacuum pipes, (check the pipe to the MAP sensor specifically) or inlet manifold gasket. This would in turn result in the lambda sensor adjusting the pule width on the injectors higher (i.e. more fue njcted to compensate for excess of air). This in turn would account for high HC and CO levels.
To test for vacuumleak, take a can of brake cleaner or WD40 and spray around vacuum pipes etc. Any rise in engine revs would indicate a leak.
Hope this helps.
There is of course the possibility that the lambda sensor is faulty, they only really have a life of 75,000-80,000 miles depending on driving conditions With your Toyo on 90k, the sensor could be switching sluggishly, and thus not responding quick enough to the rise in engine revs/pulse duration of injectors. A scope reading of the black and grey wires (assuming ts a four wire sensor). The output should oscillate between 0.2 V and 0.9V troughly at idle and level out at around 0.45 v at a fast idle. Again, this is assumin the system is air tight.

shamwari

@bansko, PM sent!

Bansko

Julio71 wrote: »

Hi, we are trialling a new vegetable based fuel additive that is proven to reduce emissions and fuel consumption.

If you are interested in taking part of this trial please let me know. If it doesn't work, we'll pay for your re-test.

Thanks.
J

Hi Julio,

I'm happy to help with your trial.. I'll contact you near the time I'm ready to take the test again.

Galwayclass

Just failed NCT on emissions........................
Engine/Oil Temp 87c
Low Idle (800rpm) CO 6.07%
HC 295ppm

High Idle (2890rpm) CO 3.87%
HC 200ppm

Lambda 0.90

From reading the posts I fear it might be a Cat jobie but could there be any other reasons for such high readings ??
Thanks