C270 smoke

[x332race]

My car has started to smoke under acceleration to an embarrassing degree. I have also noticed a slight "wandering" of revs under constant throttle between 430-65mph. Otherwise car drives well and is returning normal mpg.

Looking at other threads I should be considering

1. EGR
2. Air Mass sensor
3. Split intercooler hose
4. dirty air filter.

Any ideas ans what else should I look at?

 

[BlackC55]

Number 3 first. Rev it in P and listen for a whooshing noise with the bonnet open.

 

[x332race]

Number 3 first. Rev it in P and listen for a whooshing noise with the bonnet open.

Will try when it gets light tomorrow and report back.

 

[x332race]

No "whoosing" noise.

However, I did note that the jubilee clip around the air pipe on the engine side of the Air Mass Sensor was loose so I have tightened this up (don't know if this would cause excessive smoke but could be leaking air into the system?)

Also checked air filter and that is quite soiled (but not excessively so) so will need to change it....again don't know if this is root of problem.

 

[kwakdonut]

Process of eliminiation I think! Check all the air pipes and connctions. Get the air filter changed. Try again. Return to forum if still troubled!

 

[x332race]

Have now driven the car with the clamp tightened on the hose.....my first impressions are that there is considerably less smoke although there remains some smoke evident. At least it does not now appear to be in embarrassing quantity. Would a loose clamp on the hose just after the air mass sensor make all that difference?

I now need to get hold of an air filter and see if that makes a difference.

 

[kwakdonut]

Oh yes. Any extra air in the wrong place will play havoc with the engine.

 

[x332race]

Car still playing up.....black smoke perhaps not quite as bad as it was but still plenty there. Also when accelerating to about 2000rpm rpm wavers up and down slightly before settling indicating a problem.

Have now booked it into local indy to have it checked out on computer as we think Air Mass Sensor may be at fault. I gather that live readings have to be taken on a test drive to check if sensor is a fault?

 

[kwakdonut]

They should check live data while engine is running - no test drive should be needed

 

[x332race]

They should check live data while engine is running - no test drive should be needed

Ok...perhaps I misunderstood.....I was told car had to be running and in retrospect I realise that could be stationary.

 

[kwakdonut]

Yes, it will be stationary. I believe that STAR will run some tests which will rev the engine but apart from that, no test driving!

 

[x332race]

Is it possible for dirty fuel to create black smoke problems?......since I refuelled with Shell Optimax Diesel, the car seems to be running smoother and kicking out less black smoke

 

[Cabe]

I have experienced (and I think there is a thread on here about) Shell Fuelsave being basically crap for Merc deisels. I had a smoky exhaust, rev hunting and on really damp days, poor starting. Changed to Tesco el cheapo and all theses issues have gone.

 

[x332race]

I have experienced (and I think there is a thread on here about) Shell Fuelsave being basically crap for Merc deisels. I had a smoky exhaust, rev hunting and on really damp days, poor starting. Changed to Tesco el cheapo and all theses issues have gone.

That's interesting as my last fill ups have been Shell Fuelsave.....

Now have Shell Optimax which the car has always run well on.

 

[x332race]

Right...got really fed up with the black smoke behind my car and the hesitating at certain rpm (around 2,000rpm) so I remembered from somewhere that you can disconnect the MAF (Air Mass Sensor) it will revert to a default programme and you can see if the sensor is at fault. Anyway, disconnected the sensor and the car stopped smoking and ran correctly without any hesitation...

Does this indicated that the sensor has failed...seems sensible to me to fit a new one anyway...

How much and where is best place to get a MAF for a facelift C270?......
I should be able to get one from a main dealer but are there better sources?

 

[Justin1600]

Hi mate, if you get someone to put their foot on the brake with the engine running in drive and bring the revs up carefully so that the turbo is cutting in. You stand in front of the vehicle with the bonnet open, check for any hissing sounds from behind the front bumper where the intercooler is and from the top and bottom intercooler pipes.
Normally the top intercooler pipe splits around the back where you cannot see it ( feel with your hand, or take it off to check )
Also a injector could be faulty, or Air mass like you say. Best to get a Star Diagnostic machine hooked up to check for fault codes

 

[x332race]

Hi mate, if you get someone to put their foot on the brake with the engine running in drive and bring the revs up carefully so that the turbo is cutting in. You stand in front of the vehicle with the bonnet open, check for any hissing sounds from behind the front bumper where the intercooler is and from the top and bottom intercooler pipes.
Normally the top intercooler pipe splits around the back where you cannot see it ( feel with your hand, or take it off to check )
Also a injector could be faulty, or Air mass like you say. Best to get a Star Diagnostic machine hooked up to check for fault codes

Tried all that...all the pipes appear to be ok.......disconnecting the Air Mass seems to stop the smoke and the hesitation.

 

[Justin1600]

Tried all that...all the pipes appear to be ok.......disconnecting the Air Mass seems to stop the smoke and the hesitation.

New Air mass and a air filter then try again mate may need to check the injectors for excessive leak back with the test tube kit if the air mass does not cure it.

 

[x332race]

Hi mate, if you get someone to put their foot on the brake with the engine running in drive and bring the revs up carefully so that the turbo is cutting in. You stand in front of the vehicle with the bonnet open, check for any hissing sounds from behind the front bumper where the intercooler is and from the top and bottom intercooler pipes.
Normally the top intercooler pipe splits around the back where you cannot see it ( feel with your hand, or take it off to check )
Also a injector could be faulty, or Air mass like you say. Best to get a Star Diagnostic machine hooked up to check for fault codes

You were right...found a split in the top hose to the intercooler. Missed by the garage I took it to and by others who have looked at it.....off to merc to get a new hose now.

 

[x332race]

Number 3 first. Rev it in P and listen for a whooshing noise with the bonnet open.

Thanks for the advice.....you were correct in your diagnosis....however, there was no discernible "whooshing" noise from the engine and the split was pretty difficult to find...that's why it took so long to discover the problem. Car seems to be running perfectly now.

Any way thanks for all the advice from the forum.