NCT fail on emissions

Brian2208

Hi,

Had an NCT yesterday and the car failed on emissions. The reading was 0.39%, the limit is 0.30%. It's an 03 Micra and has been serviced in the past year, about 3000km ago.

What's the simplest way to get the emissions down? The car's been parked up for the past month or 2, the tester mentioned that it might just need a bit of driving to clean it out. Any other suggestions?

Also, on a retest are they only checking for what failed previously? The engine light is prone to coming on at times. If it's on for the retest can they fail it for that?

Thanks

biko

Put a full bottle of Dipetane in there, then drive the car hard a few days. This should clean out any deposits.


Engine light will fail diesel cars, not petrol cars (provided everything else passes)

RMAOK

I think the NCT can only check what the car failed on in the initial test - even if the light is on in the dash, so long as it wasn't noted as a fault in the initial test, the NCT can't do anything about it.

biko

No, that's not correct. They can and will fail on anything obvious they see during a retest.

RMAOK

biko wrote: »

No, that's not correct. They can and will fail on anything they see during a retest.

Oh ok, didn't know that.

biko

For OP, having car parked up a month or two will cause things to happen with engine and brakes.

When is your retest?

hondar

full bottle of dipetane into half a tank. drive it in high revs.that will clean it out after a few days.as for the engine management light,it cant be failed for the light on but you wound be as well off getting it plugged into a diagnostic and see what is bringing it on.

myshirt

hondar wrote: »

full bottle of dipetane into half a tank. drive it in high revs.that will clean it out after a few days.as for the engine management light,it cant be failed for the light on but you wound be as well off getting it plugged into a diagnostic and see what is bringing it on.

Where are you reading that it can't be failed for a light on? Of course it can.

biko

As I said above, it's a fail for diesels but not for petrols.
People tend to forget to mention what fuel type car is.

1874

dont know about the dipetane, haven't used it myself, thought I saw a suggestion of car sitting up for a while, if so don't think that helps, regular running or at least bring it for a good run and warm it up in advance, if after that it still failed I'd use dipetane myself, as your after failing already, I'd go with that suggestion and warm it.

hondar

myshirt wrote: »

Where are you reading that it can't be failed for a light on? Of course it can.

I am not reading it anywhere.i am a mechanic.
Only safety related warning lights will fail so airbag, ABS etc.

Brian2208

Thanks for the replies. I haven't booked the retest yet, think I have 4 weeks to get it done.

The car is petrol so should it not matter if the engine light is on? I should get it looked at but with a 16 year old car it probably wouldn't be economic to it fixed.

Where can I get Dipetane?

Leonard Hofstadter

As above, engine light in a petrol is not necessarily an NCT failure. Nevertheless, the light is on because there is a problem with the engine, so it still needs to fixed. If the engine light is on because the fault is something which affects the exhaust emissions then it will still fail (the emissions will be too high).

biko

Brian2208 wrote: »

Where can I get Dipetane?

Several motor factors will stock it, or similar products.
Ring a few local places and ask.

w211

Old car can have a load of problems. First you need to find a guy with tester and read the live data. If there is any fault code present then you can get the hint from there what is wrong. Not every code start the "money lights" on the dash. I use my scanner and it is much easier to find a problems than just guessing.

Before any investment to old engine repair, please check the compression first. If there is problem, then it may cheaper to buy an new engine.

Check your spark plugs. If these are old, you need to replace these. To do it only by cold engine, because otherwise you will damage the cylinder head.

Replace the all filters. It is important to replace the air intake, fuel and oil filter.

Did you replaced the engine oil and filter before NCT? If you to do it days or week before the NCT you can get a very good result. The cheaper way to fix the engine are to clean it every while.

If fuel filter are old, it can reduce the delivered fuel pressure and all injectors works poorly.

Clogged air filter can cause load of problems, change it every year.

Buy MAF cleaner and throttle cleaner. Clean the MAF and throttle. The next easy step are to find any vacuum leak. If your car have a big vacuum leak then it idles raw. There is several way to test the vacuum. I have for that purpose the smoke machine. The cheaper way are to test the vacuum are to use brake cleaner, propane (very dangerous) or water. The last on is easy to use but you can not soak the engine. The test is easy, apply little bit the "test fluids " to intake collector, intake hose or vacuum lines. You can detect the vacuum leak if engine sounds different after apply the "test fluids". If engine RPM remains the same all the time, you have no vacuum leak. Like I said, do not soak.

So funny it sounds, check the car battery health too. All modern cars depends heavily about the good power source. Also check the alternator output.

The next part need again the scanner because you can not see the short and long term fuel trims or O2 sensor values without that. Example my car need soon the new O2 sensor because these are not switching properly. O2 heaters are ok but switching vales are too low. Without scanner I could not detect it.

The engine may need to check the timing too. It can be the off from marks. The belt/chain can worn out and need to replacement. Never replace the belt/chain only. Always change the tension/idle pulley too.