2001 CDT MOT fail, excessive smoke

[badrover]

My CDT has failed its MOT on "exhaust emits excessive smoke or vapour likely to obscure the vision of other road users".
Basically, under normal load and at idle it's fine but when you boot the accelerator it emits a cloud of black smoke. Knowing this may be an issue as it was mentioned the previous time, I changed the PCV filter (which was fine and only done 5k miles), air filter and visually inspected the MAF sensor. I've also experimented with unplugging the MAF but it seems to make little difference to the smoke.
The inter cooler O rings are less that a year old (Viton), the car really performs well (standard 116bhp), pulls like a train, has an EGR blank and has done 119,000 miles. Incidentally, the smoke is black so it's definitely fuel related.
Where should I be looking next?
Thanks.

[bl52krz]

I know you have changed the rings on the intercooler, but have you checked the pipe for any ‘soft’ spots? The pipe could be collapsing under acceleration .Easy enough to check. Also could be a tear/rip in same.

[johnnyb44]

Hi.
It's a long shot but why don't you try some Forte diesel/ injector cleaner. It's like a stronger version of Redex and it will really clean you engine out. Last year my emissions were 0.91 without the use of Forte. This year after using it, the emissions were 0.71 at the Mot the other day. It maybe worth a try. You also really notice a difference in its general running. Mine now feels somewhat livelier and notably smoother.
What ever you decide I hope you get it sorted buddy.
All the best,
Johnny. :-)

[badrover]

Thanks. The MOT guy checked the intercooler rubber hose and said it was maintaining pressure when it was revved. I'm going to remove the bumper at the weekend regardless and check it all over though. I've got a spare set of o rings so will replace them regardless. Just think it makes sense to double check the cheap things first.

[75c]

no doubt an expert will have a better idea but when mine did this it was a kerfuffed turbo

[badrover]

I hope not as that might signal its demise. I'm pretty much at my whits end with it as I spent a fortune on suspension components and new tyres in an attempt to get it through the MOT. I'll be drawing the line at a new turbo. I did check for play when I removed the MAF pipe and there was zero so fingers crossed its ok.

[badrover]

Thanks Johnny, good suggestion. I run a fuel treatment through every 12 months or so though. It had forte just before the 2017 MOT and has just had some comma so should be ok.

[Kev75]

Italian tune up!!!!!
Kev

[badrover]

Originally Posted by Kev75

Italian tune up!!!!!
Kev

Done that too, really gave it a good blast!

[rovertone]

Originally Posted by badrover

Done that too, really gave it a good blast!

When you say 'gave it a good blast' was that road speed or engine speed. I went through several years of passing the smoke test because my friendly garage only 'tickled' the revs to get a pass. For this year's MOT I put a bottle of |Forte cleaner into under a quarter of a tank and ran the engine at 3500-4000rpm (in 3rd!!) for about 5 miles. My garage wanted to know what I had done this year to get such a vast improvement, passed easily.

Moral of my tale is my blast prior to MOT was at 70/80mph when I should have been an engine blast. Up to this year, like you, I had checked and double checked everything including suspecting the turbo. Because I only drive light footed I can still get black smoke under initial hard acceleration but will be repeating the aforementioned process next year.
Good luck.