MOT Failure Help/Excessive Smoke

[design guru]

Well after months of stressing about the SRS light being on 2 days before the MOT the light switched off by itself. Its done this in the past but as soon as someone sits on the seat it comes back for a few days. I had it diagnosed and the seat sensor is the cause.

I took it for the MOT and it stayed off and there was no mention but it did fail on the exhaust emitting an excessive level of metered smoke for a turbo charged engine (4.64 1/m)

I have a retest in a few days but any ideas on how to resolve this issue please?

W220 S320cdi 2001

 

[ivan1983]

What sort of driving do you do?

If its mainly town then its been said that a blast on the motorway giving it plenty of beans has been known to clear up smoky diesels for the MOT test.

The Italian tune up has been know to fix many a problem.

Others may chime in with more useful comments, possibly a clogged EGR valve?

 

[design guru]

May do a fuel filter change as this maybe long overdue and possibly needed by now. Is this a simple task or am I risking it?

Are there any special tools required?

Are there any good write ups that can direct me to a starting point in the How to section.

 

[mersum1es]

Check splits in air hoses, is the turbo actuator moving, blocked intercooler, bad injector? (plus EGR system already mentioned)

 

[Dieselman]

How many rev cycles did they give it?

Do you notice black smoke when driving?

As long as it hasn't been chipped then a dose of injector cleaner and a good thrash should fix it.

 

[pugilist]

Turbo on its way out possibly.

 

[design guru]

Turbo on its way out possibly.

New turbo fitted 3 months ago, mainly when I kick down it chucks out cloud of smoke. I didn't use the car on the weekend that much and just started the car and drove it straight to the MOT. only 5 minutes away. I think some cleaner a good run before the retest should be OK.

Will do an oil change along with new air and fuel filter on the weekend.

 

[design guru]

How many rev cycles did they give it?

Do you notice black smoke when driving?

As long as it hasn't been chipped then a dose of injector cleaner and a good thrash should fix it.

the smoke only appears if I floor the pedal and it revs quite high, on a normal kick down it does not chuck out smoke, but the response is instant so no issues there. I am starting to think its the fuel filter as this has not been changed since the 30k I have done since owning it and who knows when it was last changed.

 

[Agwarn]

Has the air filter been changed recently?

 

[Dieselman]

If there is any fault I would think it is the EGR valve sticking open.

 

[design guru]

Air filter was changed, but before the turbo was replaced and fumes were leaking in the engine bay so I will change that on the weekend along with the oil and other filters

 

[design guru]

If there is any fault I would think it is the EGR valve sticking open.

I did think the EGR valve could be a possible reason so hopefully I can have a look when I do a service. How easy is it to access and remove the EGR valve?

Can you recommend any good tips or guides?

 

[1001ab]

+1 for the Italian tune up.
I got a nice gold star from my Mother in Law for taking her smokey W211 E320CDI for a motorway run using the manual 'box controls to hold it higher in the revs. I did about 40 miles and that cleared it up. She thinks I did something complicated and technical.
I got the tip from the local Indie MB specialist while I was looking for a C320CDI a few years ago. Lots of people I know with diesels they probably shouldn't have bought (they do under 10k miles a year, mostly in town driving) have been given the same advice when they ask the dealer about the smoke.

 

[tjamesbo]

If there is any fault I would think it is the EGR valve sticking open.

+1 for the above Mine was stuck open and was smokey on acceleration its now shut courtesy of Alex Crow and EGR delete Mod has been done so no future EGR Problems .
Boyd

 

[design guru]

I did add Redex and gave it a blast, it sorted the problem and passed the MOT, surprisingly it reduced the emissions reading by half. The main problem I had was finding an open road when nobody was behind me to floor it and release the mushroom cloud of smoke.