Smokey V6 E320cdi


Senior Member
Jul 3, 2008
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Your Mercedes
2007 E320cdi S211, SL320 2000(written off), Lotus Excel
Hi folks

I have a 2007 E320cdi cdi with the OM642 engine and 222k miles on the clock. The car’s been off the road for about 5 months due to an issue with the brakes and no time to fix at that time.

I’ve now sorted the brakes and getting car ready for MOT, but it seems a bit smokey, so not sure it will pass emissions. On initial start and idle there is no smoke on stating from cold, but can be a little when started from hot.
if revs are raised slowly to 2,500 there’s very little smoke, but if revved and held at max revs, which I believe is how the smoke opacity is measured it is quite smoky. It will then continue to smoke at idle for about 10 minutes, but appears to clear. I’m not great at colours, but to me it is white with a hint of blue. I have added a video of this.

So far I have
Serviced it with new oil, oil filter, air filters and fuel filter.
I have access to STAR and -

there are no fault codes
Before I serviced it I used the automatic EGR test and this appeared ok with Lambda just out at 95% EGR - photo attached. When I carried out the service I reset adaption values, but chose all, rather than just air filter. Now when I try to do the same test, STAR won’t let me as lambda stays at 0 and doesn’t change. F3EB79EB-FD55-4DF8-9FC3-6E2C2883588B.jpeg

The Lambda sensors on this car have me confused. I only have one, which is post cat. There is no pre-cat sensor ( I also don’t have a dpf). Yet on Star it shows this sensor as G3/2 (O2 sensor upstream of KAT) double checked by unplugging it which gave a code for G3/2.
I have done a test on this as far as the heating circuit and this is within tolerances, but other than reading the value via the EGR test, I don’t know how else to test.

Is this now staying at 0 as adaptions reset and car needs to go through some drive cycles, or is it likely it was on its way out and it’s now unable to adapt? This, however doesn’t appear to have made any difference to smoke.

I have also checked compression via Star - passed
Checked injector correction quantities, and they are all good
Checked operation of swirl flaps - passed
Checked turbo electronic actuator - passed
Also last year I had the infamous oil leak from the heat exchanger in the engine V. I stripped everything down and replaced these. I also fitted a new swirl flap motor as previous one dead, cleaned out inlet manifold and replaced rods that control swirl flaps with the metal ones. All gaskets etc were replaced and were genuine Mercedes.

I have disconnected the breather hose - again no difference to exhaust smoke. A video of the smoke coming out of breather-

So, my questions are - is it likely to fail MOT with amount of smoke and where should I be looking to reduce it? Also should I be replacing O2 sensor?



Senior Member
Dec 26, 2006
Reaction score
Sutton Coldfield, West Midlands
Your Mercedes
1999 CLK430, 2007 VITO 3.0V6 , W124's (1994 320TE , 1993 220TE ) , 07 2.5 X-Type
How Did you get on My 639 with the OM642 in it failed ( see my current post ) any info /tips gratefully received

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