Failed NCT smoke test

Nuttzz

So my Alfa GT 1.9 Diesel failed its smoke test.

I read here that I should get an additive for the engine and take it for a good hard drive

So here is my question, what would you call a good hard drive? Drive on the motorway in 4th at 120km/h for a bit? Any advice appreciated

223vmax

Yes & dipetane.

shietpilot

Just drive it happily through the gears, don't shift early. Rev to 3800 RPM shift up and repeat a few times. You will probably see it puff smoke out for a bit and then it should stop. If not then you have other problems.

biko

It depends on why it failed the smoke test

If we look in the manual https://www.ncts.ie/media/1004/nct-manual-july-2014.pdf there are several reasons it can fail, see page 10 onwards.

But yeah, wait until car have reached operating temp and then drive it on the motorway. You don't have to drive fast, just keep revs at 3500 - 4000 rpm for 30 mins or more.

Again, car MUST be at operating temp before you start this.

What additive did you think of using?

Nuttzz

I got a bottle of dipetane, the NCT guy said get dipetane and rev through the gears, he was pretty sound about it in fairness

biko

Drive it like you stole it

You really want to give it a good workout, it's an Alfa after all

JohnCleary

biko wrote: »

Drive it like you stole it

You really want to give it a good workout, it's an Alfa after all

^^ This.

Redline the sh1t out of it on the way to the test :pac:

biko

Me, I would start with a full tank of fuel with a full bottle of Redex fuel system cleaner poured in a week before the test, then drive like crazy for a few days.

On the day of the test pour a full bottle of dip into what's left of the tank and take it for a 30 min drive just before test. You want car to be red hot when you arrive at the test centre.

Since you haven't told us what it actually failed on I am just suggesting things - it may work, or not.

Del2005

Nuttzz wrote: »

I got a bottle of dipetane, the NCT guy said get dipetane and rev through the gears, he was pretty sound about it in fairness

What happened to fixing the problem instead of sticking a band-aid over it. A garage suggesting driving it is bad enough but when the tester is it shows how little people worry about filthy diesels pumping noxious gasses into everyone.

jca

Del2005 wrote: »

What happened to fixing the problem instead of sticking a band-aid over it. A garage suggesting driving it is bad enough but when the tester is it shows how little people worry about filthy diesels pumping noxious gasses into everyone.

There's probably nothing wrong it. It just needs a good work out to clear out all the town driving crud.

grogi

Del2005 wrote: »

What happened to fixing the problem instead of sticking a band-aid over it. A garage suggesting driving it is bad enough but when the tester is it shows how little people worry about filthy diesels pumping noxious gasses into everyone.

A diesel smokes when there is too much hydrocarbons in the mixture. This is typically caused by an injector that does not close completely because of residues. When you drive the car aggressively for a while, those residues get removed/burned and the smoke levels are reduced.

Of course there are other reasons for that - a broken sensor might cause it too. But it's much less common.

NOx is a different story, and those get produced when too much oxygen is in the mixture... It is a balancing act, with a lot of advancements in the post-treatment as well.

In general - diesel engines don't like gentle driving. Injectors, DPF, variable geometry turbo - all need to be pushed a little from time to time to work correctly...

Nuttzz

biko wrote: »

Me, I would start with a full tank of fuel with a full bottle of Redex fuel system cleaner poured in a week before the test, then drive like crazy for a few days.

On the day of the test pour a full bottle of dip into what's left of the tank and take it for a 30 min drive just before test. You want car to be red hot when you arrive at the test centre.

Since you haven't told us what it actually failed on I am just suggesting things - it may work, or not.

Cheers, it failed on Smoke 6.17/M to be exact

I'm a very gentle driver and never run it beyond 3000 rpm for more than a few moments so it maybe just city driving crud

Nuttzz

Just to update

Got the dipetane and took the advice here and drove on Saturday from the Red Cow to Kildare village at about 3500 rpm

Did the retest this morning and the smoke reading was down to 1.44/m so a massive drop

Thanks to all for the advice and hopefully this thread will be useful to someone in the future if they search for it

vandriver

Nuttzz wrote: »

Cheers, it failed on Smoke 6.17/M to be exact

I'm a very gentle driver and never run it beyond 3000 rpm for more than a few moments so it maybe just city driving crud

If you are on a straight empty road,floor it in first and watch your rear view mirror!
Gentle town driving just accumulates soot.

biko

biko wrote: »

........
On the day of the test pour a full bottle of dip into what's left of the tank and take it for a 30 min drive just before test. .......

Exceeding recommended dose of dipthane is a waste of dip', there's zero benefit.

flanders2006

I recently faild the NCT on emissions of 2.44, should be below 1.5, and have it booked in to garage as brake pipe is loose also. Would the Dipetane likely sort me out?

2010 Mondeo

easygoing39

Dipetane worked on my 2008 Mondeo ,that and being driven hard for a week leading up to the retest.

knipex

Del2005 wrote: »

What happened to fixing the problem instead of sticking a band-aid over it. A garage suggesting driving it is bad enough but when the tester is it shows how little people worry about filthy diesels pumping noxious gasses into everyone.

I wonder ???

Nuttzz wrote: »

Cheers, it failed on Smoke 6.17/M to be exact

I'm a very gentle driver and never run it beyond 3000 rpm for more than a few moments so it maybe just city driving crud

Yup there it is.

You sir should have a petrol.

I have a diesel golf 260k km. 50 60k km per anum. Driven on a motorway every day 120 to 130kph. Driven as a diesel is meant to be driven. Oil and filter changed every 12k km.

NCT last week.. smoke reading .... 0

ERG valve never touched, DMF never touched, DPF never touched..

If you have predominantly city driving. buy a petrol.
Regular short trips.. Buy a petrol.
under 40 to 45k km per annum ? buy a petrol.

Do the environment, the population of your town and your pocket a favor.. Buy a petrol..

grogi

knipex wrote: »

Do the environment, the population of your town and your pocket a favor.. Buy a petrol..

That's not that easy... In majority of cases petrol is only in the cheapest form. Add some gadgets, add automatic - and the only option is a diesel.

knipex

grogi wrote: »

That's not that easy... In majority of cases petrol is only in the cheapest form. Add some gadgets, add automatic - and the only option is a diesel.

For which you can blame the greens.. And the subsequent reduction in urban air quality....

grogi

knipex wrote: »

For which you can blame the greens.. And the subsequent reduction in urban air quality....

I do. The CO₂-based-only taxation should end. But don't tell the man to buy a petrol when often there isn't one.

biko

Don't revive old threads unless you have already posted in it last time and want to update it, thanks