nct fail 3 times

cena

hi. i'v just had my 3rd test again on the emission test. failing on high idle

have put in a new lamba and new cat. the guy that tested the car said the cat seal mite nt be on right on air could be getting in.

does anyone have any suggest on what could the problem

Darragh29

cena wrote: »

hi. i'v just had my 3rd test again on the emission test. failing on high idle

have put in a new lamba and new cat. the guy that tested the car said the cat seal mite nt be on right on air could be getting in.

does anyone have any suggest on what could the problem

Can you post your test result data up here???

Also can you post up the temperature that they test was done at, it'll be on the sheet???

cena

EXhaust Emissions
engine/oil tempertaure 89 c

low idle co o.o5vol%
820 rpm hc 0 ppm


high idle lamba o.986
2800 rpm co o.50%
hc 37 ppm


it say its above 2% on the highe idle.

its down one 1% since the last test

Darragh29

What is the make & model?

cena

its a 02 punto.1.2 8 vavle

Darragh29

The problem is that the engine is running too rich. I wouldn't say there is a problem with the cat being sealed because if there was, there would be excess oxygen in your exhaust at high idle which isn't happening, and in any event, you have the same problem before and after the cat was replaced, which points to the problem being something else.

You'd really need to connect the car to a diagnostics system and look at real time data being generated. Where I've seen this problem before, the cause was:

Coolant temperature sensor returning an incorrect signal, causing the engine to run rich as the system was getting in incorrect signal back from the coolant temperature sensor, and making fuel adjustments on the basis of believing that the engine was still cold when it was actually warm.

I've also seen this problem once being caused by a perished vacuum pipe coming from the inlet manifold. This caused excess oxygen to enter the inlet manifold which was detected by the lambda sensor, and returned data to the ECU which resulted in more fuel being horsed into the system and picked up in the exhaust tract which is the problem you are having. This problem can be caused by air leaking in anywhere in the inlet area, once it is upstream from the lambda sensor, such as the inlet manifold, etc...

You'll really need to connect up to diagnostics first and look at sensor signal data first, unless you can find an air leak...

atlantean

Good info posted above ^^^

Another option - have you tried Dipetane? I am not a believer in fuel additives but this fuel treatment does what it says on the tin

cena

what do u mean by running too rich. how much would it cost to get it hooked up to the computer at the main dealers

mick.fr

Just get a bottle of Fuel injector/carb cleaner from Halfords or else.
10 quids or so.
Inject by small pressure small quantities (1 push at a time, 5-6 times, wait a good 30 sec each time) directly into the air intake pipe (Must be opened without the filter).

Alternatively you can do a seafoam cleaning, very effective.

Darragh29

cena wrote: »

what do u mean by running too rich. how much would it cost to get it hooked up to the computer at the main dealers

Your engine has what is known as an ideal air:fuel ratio. What this means is that for every 1 part of fuel you want to burn, you need 14.7 parts of air by volume to completely burn that 1 part of fuel. When these conditions are met in your engine, your lambda value will be 1.000, which is ideal, or very close to that value. If your lambda value is higher than 1.000, you have more than 14.7 parts of air for every part of fuel being burnt. If your lambda value is less than 1.000, you don't have enough air to burn that 1 part of fuel.

This is a very simple explanation of what is happening. When you don't have enough air to burn the 1 part of fuel, this has consequences for how these gases re-combine after combusion as products of combustion and one of these consequences is the generation of excess amounts of CO (Carbon Monoxide).

As all this is a dynamic process, you won't get ideal values so the NCT have set up a range for lambda values which your car lambda result must fall inside in order to pass. If your lambda value at high idle is between 0.97 and 1.03 then this is a pass. As you can see, your lambda value is below 0.97 so this is a fail.

Darragh29

http://en.wikipedia.org/wiki/Air-fuel_ratio

Mr.Diagnostic

But he said that lambda is .986 which is within spec.

Darragh29

Mr.Diagnostic wrote: »

But he said that lambda is .986 which is within spec.

Your right, whatever way I looked at that data I thought it was .86 or something starting with a .8.

Mr.Diagnostic

The gasses and lambda figure that are tested in the NCT are the only reading available to the NCT tester. These reading are not enough info to form an educated opinion of the cause of an emission failure.
Likewise, posting those figures here is not enough in a lot of cases. This is one of those cases. A good diagnostic tech would have access to more info on his/her gas analyser along with the other equipment required.

cena

i.ll bring back to the place i got the cat and c what they have say. hopefully its somthing simple

Darragh29

Did you tell them before you got the cat and lambda sensor changed that you were having this issue with the NCT? I'd always have done an emissions test in-house after fitting a cat or a lambda sensor, I'm not saying I've all the answers but I just used to go to extraordinary lengths to make sure I had my ass covered and I didn't have a customer coming back to me for anything!

I've also seen it where a car isn't warm enough (even though the oil is strangely enough!), where you get this lack of a response from the cat as the cat only starts working when it is hot and this usually requires a drive or a period of revving the engine for this to happen. You've failed the NCT 3 times now though so I doubt this is just down to temperature.

I think you need to get it plugged into a diagnostics tool and look at the data being returned from engine sensors. I imagine by the time you get this resolved, you're be back into full NCT re-test territory because if you don't get your fail items sorted out and retested within 28 days, you have to do the whole full test again...

cena

have test again on friday. give me little to sort out. had told them that i failed on the emissions