Diesel Emissions (not the VW Scandal!) - VW Forum - VZi, Europe's largest VW, community and sales

cbst3 · 21-01-2021, 04:13 PM

My old Toyota Yaris Diesel, now run by my daughter, had it's MoT today and failed only on the emissions. It's a 2007 model so no DPF as far as I know and it failed on the smoke test, with a 1.09 against a 0.8 or lower pass rate. Started out at 2 ish, so came down a lot during the test itself.

Tester told my daughter to drive 4-500 miles and then bring it in, but that will be difficult as the old MoT has lapsed. Other suggestion was to sit on the drive at 4500 rpm for an hour, which I am sure our neighbours would love!

Any suggestions? I was thinking a bottle of Redex emission reducer and a decent run with lots of high rev action would do the trick?

Hoosier · 21-01-2021, 04:32 PM

A strange thing for the tester to say.
Book it in for a retest.
Half hour to 45 mins before the test, take the car for a decent run up the local bypass or junction of motorway. Then straight to the test centre piping hot.
Job done.

mocco · 21-01-2021, 05:10 PM

Change the fuel filter for a new one and fill the new filter up with a good injector cleaner. Start the engine and give it some revs and like said get the engine nice and hot before having it retested

cbst3 · 21-01-2021, 05:23 PM

Thanks, much appreciated.

Last Triumph · 21-01-2021, 06:43 PM

Quote:

Originally Posted by Hoosier

A strange thing for the tester to say.
Book it in for a retest.
Half hour to 45 mins before the test, take the car for a decent run up the local bypass or junction of motorway. Then straight to the test centre piping hot.
Job done.

This ^

When they rev it up in the test, it blows a load of built up soot from the exhaust out with the regular emissions. This needs cleaning out and the easiest way to do this as suggested - get it hot, then several full pulls in 2nd and 3rd gear - you'll see the grey haze behind as you do so which will begin to clear after several pulls. Once clear, then take it for the test.

This is a regular thing for our Golf tdi every year as it only ever does local driving at low revs so never gets a good clear out.

A good blast should clear it.

RaggedyRacing · 21-01-2021, 06:54 PM

An Italian tune-up

You MUST wear a bolognese stained vest while performing it

Last Triumph · 21-01-2021, 07:59 PM

Quote:

Originally Posted by RaggedyRacing

An Italian tune-up

You MUST wear a bolognese stained vest while performing it

Crasher · 22-01-2021, 10:16 AM

Fit a less restrictive air filter such as a K&N, this allows more air in and reduces smoke. Be wary of some types of oiled filter where a hot film air mass meter is used but K&N panel filters have never given me this issue.

Bada Ben · 22-01-2021, 12:10 PM

Even a new stock air filter will help if the old one is getting clogged.
As previously mentioned, it may need a good run to clear-out soot. This made a big difference on my old Passat Diesel.

cbst3 · 22-01-2021, 03:54 PM

Just gave it a good run, exploring the upper reaches of the rev range, which isn't a nice place to be really - it's not the most refined diesel...

It's now back at the test station, and they are going to do a test without logging first, so if it doesn't pass this time, we haven't used our one shot retest, which is good of them.

If it doesn't, I'll fit a new air filter and try some fuel system cleaner. I am hopeful though, it's not a smoky car, I've had it from new and it's been driven quite hard, but not from cold, and not abused.