Smoking V70 D5 2001

[Shocktube14]

Thanks for your reply.

Its definetly grey smoke NOT blue.

If you could look through VADIS that would be great.

Cheers.

Richard.

[Retired MVS Contributor]

He mentioned the grey-ish smoke as well, which could be oil that is NOT being burned in the engine (which would be blue) but rather from the hot side of the turbo leaking into the exhaust.

But then he later mentioned the excessive fuel consumption.

We don't have the diesel versions over here, but generally you can unplug the mass airflow sensors on the gas engines. If the idle/black smoke smooths out, that means the sensor is giving an incorrect reading and dumping too much fuel into the engine.

Vacuum leaks can cause over-rich conditions as well, leaky injectors, or a terribly clogged air filter/leak in the turbo hoses.

I'm not sure what other sensors there are in a diesel engine, but I can try to take a look through VADIS for you when I get home.

JB

No boubt oil is burning too!...But the black smoke during acceleration is a strong indication of incomplete combustion...I already checked Vadis and find nothing covering diesels...Could be because it is a US version of Vadis, I guess...Something in the back of my mind that goes 'way back tells me there is no MAF because diesels inject directly into the combustion chamber, not the intake manifold...I would think that the control system and sensors are entirely different because the operating principle of the engine is different...For instance, there is no ignition system, no spark plugs, no coils, etc....

ST

My limited experience with diesels was with industrial engines...BIG!!! industrial engines and it ain't the same...
If the injectors were clogged, it would be starved for fuel, would be hard to start, and would have no power...Since it is blowing black smoke, it would seem to be because leaking injectors are passing too much fuel...The tips of the injectors are right in the combustion chamber and coke up after awhile and that breaks the intended fine spray into a dribble that does not ignite...I believe that there are diesel injector cleaners available that you run through the system...If not, I would try removing them and cleaning them up...

Jerry

[jblackburn]

Modern diesels do have some method of metering air - though I don't think they care much about the result of the burned fuel, thus your car not noticing that the exhaust is so rich.

D5Engine.jpg (224.68 KiB) Viewed 3797 times

I found this picture online. Here's the mass airflow sensor. Quick test - unplug it and go for a quick drive and see what happens. Your car may not run at all with it unplugged; I don't know how these will react. You will throw a check engine light for sure, but it can easily be reset with an OBD tool (many parts stores here will do it for free).

You may want to head to a VW TDI forum and read about some of their issues. Not many of us have much experience with diesels, as you can tell. Though the new TDI is a fantastic engine. In a couple posts I just read, most suggest either a MAF sensor, old injectors, or a boost leak - you may be on the right track with the turbo hoses

[ed7]

Yes modern diesels do monitor air flow, but do not restrict or otherwise control air intake. Fuel is metered, not the air.
Leaking injectors or incorrect timing are a likely cause of this rich black exhaust.
This is a job for an expert.
As they say, timing is everything and considering the complexity of todays modern diesels, this should be checked out by a diesel shop equipped for such. Vacuum in not in the diesel vocabulary, it is developed by a vacuum pump and used solely for brake boosters and vacuum motors in the cabin.
This is a Volvo diesel and the VW diesels of old do not apply in this case. The VW DT26 was mechanically injected and timing was relatively easy to adjust. I had one of these in a 745TD; a pretty good engine.
Ed

[Retired MVS Contributor]

I just found this in Vadis while researching a different problem...

A partially clogged fuel filter in diesel variants can cause black smoke by creating a vacuum in the pump suction line, causing cavitation...

Jerry