Advice needed please. Failed NCT

Was the engine heated up fully before bringing it to the test center? Like a 30KM drive before it.

“NCT frequency and test due dates

Private cars must undergo a roadworthiness test when they are four years old and every two years thereafter until their 10th anniversary. After that they need to be tested annually.”

Why are you getting an NCT?

Poster said that the emissions were outside the limit - hence all the discussion around the Diptane. The following points might be of interest to Bob:-

1) IMO you failed the test -re emissions- because you drive the car very slowly and you probably do short journeys most of the time - maximum 5km to and 5km back. The engine is nearly warm when you stop the car. That kind of driving is the ideal environment for the build up of carbon deposits in the engine firing/exhaust system and that leads to the failed test.

2) the Diptane along with a very hot engine while driving helps to dislodge the carbon buildup. I wonder - if you had the time if going through two bottles of Diptane might be even more effective.

3) Afull tank of fuel with Diptane will do ,say, 300 miles. IMO you do not have to do the 300 miles at high revs so as to get the engine very hot . You could spurts of, Say, 5 miles now and again And somewhat slower in between. If you are worried about the car overheating then just watch the temperature gauge

4)there are two types of diptane - one for diesel engines and one for petrol engines . Make sure you have the right one

5) as an above poster said ‘ read the instructions on the bottle’. From memory it’s a full bottle of Diptane to a full tank of fuel. Next time when filling up , ideally, put the Diptane in first and then the fuel.

6) as already said , arrive at the centre just before the appointed time having driven the car for the last ,say, 5km at high revs.

I am open to correction but that is based on my experience. Hope that has not confused you Bob

Maybe the OP bought the car 3 years ago but it wasn't new at the time.

I failed test years ago because of a clogged exhaust and a low engine temperature- ever since I’ve arrived at the NCT centre with a red hot engine 😀- it really does make a difference- even a few months ago on a freezing cold day, I remembered that I hadn’t run the engine much over the previous months (second car hardly use it) so went for a good drive and made sure the temperature was way up - saw some deposits come out of the exhaust as it got to temperature so we’ll worth doing that before your NCT- haven’t failed an emissions test since

Warning flags for me where Qashqai and mechanic saying they aren't driving it enough..I'd put money down its a diesel.

What year is the car? What's the reg year?

''4)there are two types of diptane - one for diesel engines and one for petrol engines . Make sure you have the right one''

Wrong.

There is only one 'type' of Dipethane, and can be used with petrol, diesel, and home heating oil.

I failed on emissions one year. My mechanic couldn't find any issue. It was low mileage.

Drove 20km on the motorway in fourth gear at 100kph before the retest, so the revs were high.

Emissions score were perfect second time round.

I went direct to the NCT after the drive.

2000 Nissan Qashqai? Is this a wind up?

Happy days. Just spotted this on the main page. I do a lot of town driving so changed to a small (old) petrol car, and regularly add diepetene to my weekly fills. There's a little set of markers on the side of the bottle (1 mark per 10L fuel), but don't worry - you can't really over fill.. it's just an additive.

Great for cleaning all engine components.