W169 A160 CDI smoky

[nsmorgan]

Hi, My 2005 W169 A160 CDI is pretty smoky. If I disconnect the MAF sensor, the smoke goes away and engine runs/drives perfectly. Maybe I should look at the EGR valve?

 

[V6Matty]

As you say, you disconnect the MAF and the smoke goes away, I'd personally start with a new MAF

 

[Steve@Avantgarde]

Personally I would start getting the fault codes checked and having a look at some actual values.

Diesel engines are not a hot film system like on petrol engines, so disconnecting the MAF shouldn't do anything except but a low base air volume default in and put it into limp mode.

 

[nsmorgan]

Nope, MAF was the first thing that got changed.
Doesn't go into limp mode with MAF disconnected - if anything it runs better. I think the MAF might well be hot film, but it has a ceramic PCB with some digital electronics on it.

 

[Steve@Avantgarde]

Its not a HFM MAF.

 

[umblecumbuz]

Disconnect the MAF on my 646 engine (which I did regularly while wiring in and testing my EGR delete circuit) and there is no limp mode. EML comes on. Guess there are variations between diesel engines.
You mentioned an inbuilt pcb - is your replacement MAF a Pierburg?

 

[Wighty]

Does your car do any decent motorway runs to get it up to temp and burn all the cr#p out .

 

[nsmorgan]

The replacement MAF was a Siemens, allegedly pretested. It is had the Italian Tune Up (70 mph in third on the motorway), this provides a temporary clean, but doesn't last.
I am guessing here (v diff to get real tech info), but I think the MAF maybe sends a digital pulse width modulated signal back to the ECU.

I think disconnect/reconnect the MAF is a red herring and ECU might be trying to compensate for something else, ie EGR or fuel pressure sensor?

 

[Steve@Avantgarde]

If you take it to someone who has STAR you will be able to check the operation of every single component on the charge air system.

So far you are guessing, and guessing does not fix cars, unless you are lucky.

 

[nsmorgan]

Many thanks to everyone who posted. I will post the solution when I have it

 

[nsmorgan]

Smoke problem now fixed, thanks to the good guys at MBS Southampton.
Problem appears to have been faulty vacuum pipe to the EGR.