Black smoke is normally an indicator of a very rich fuel mixture. The 940 was known to have problems with the fuel pressure regulator. Also while you are looking around under the hood, check for any of the hoses from the turbo charger and the intercooler for holes. Especially the one at the intercooler on the drivers side. They tend to rot out on the bottom causing the boost pressure to be to low to handle the amount of fuel being injected.
If it is a turbo, the turbo needs attention. Bearings? Oil leak? Worse?
It could also be cauesd by the Brain box and air flow meter. So, you also need to make check-ups on those parts.
Turbo chargers that have shaft/bearing problems blow light blue almost white oil smoke, so you can pretty much rule out the turbo itself. The "Brain box" has never been known to cause this on any 940 series Volvo, that pretty much puts it out of the situation for now. Mass air flow sensors/mass meters on turbo 940s usually cause a lean mixture problem not the "black smoke" rich mixture unless the lining of the air filter housing has came apart and the air passage through the mass air flow sensor is blocked. This would give the same problems as the hoses having holes or leaks in them that I spoke of in my first answer about low boost pressure. One very unusual time I experienced a very defective oxygen sensor to cause black smoke. That can be easily checked by connecting a volt meter to the single wire lead of the oxygen sensor and look for a voltage swing from .1 to 1.0 volts. The green wire coming from the computer supplies .5 volts of reference voltage so the sensor moves plus and minus of that voltage as it reads the content of the exhast before it passes through the catalytic convertor. Please don't forget to montior the fuel pressure! In psi it should be around 43. In bars it should be around 2.9. This is of course just my thoughts based on what I have experienced over my past 30 years at a Volvo dealer. Hope this helps.
A customer's auto is producing blue exhaust. What could cause this
There are many things that could cause your exhaust temperature to be high. Your exhaust may be plugged for example.
An exhaust leak could do that.
blown turbo - worn turbo bearing causing oil to suck through and into exhaust manifold - results in no power and neat oil burning in the exhaust - major black smoke
It could be timing is off. Need more info. Is it Fuel injected or Carburated? Exhaust smoke? Is it black? Black indicates alot of carbon built up. May mean the fuel is burning way to rich.
Could be EGR Valve.
Exhaust gasses are escaping through a hole or rotted section of exhaust system
It could, if it's leaking.
Figure out the cause of the fault, first. It could be physical, or it could be a matter of programming. These things require diagnosis to identify and isolate the exact problem in order to fix them. From my experience with Volvo trucks, they can be an electrical nightmare, and your problem is probably a short in the wiring somewhere.
Could be a diesel? If not then replace your oxygen sensor on your exhaust. A bad oxygen sensor causes the exhaust smoke to be dark in color.
They could be a cause, but you should get checked. Black feces could mean internal bleeding
Yes, those exhaust gases are extremely hot and can cause the alternator to overheat. Not only that but that carbon monoxide can enter the vehicle and kill you.
This can be caused by the exhaust valve being either bent, worn or not seating properly. If this is the case then get this checked out A.S.A.P as this could cause severe damage.
If it's the inside of the exhaust that's black it could be caused by burnt oil in the engine.
Yes, it could restrict the exhaust and cause problems
The petrol holder could leak and a spark could ignite it. The hot exhaust pipe could also cause petrol to ignite.
If it is running loudly then there is an exhaust leak either at exhaust manifold or some where else in the exhaust pipes. Bad exhaust muffler could also cause this. Hope this helps.
It could just be condensation which forms in the exhaust system outside of the engine, or you could be leaking coolant into your engine (typically via the head or intake manifold gasket).
check the exhaust system
a dining sound could be lose nuts on the exhaust
Could be as simple as a loose or bad fuel cap.
Do you have your terminology right....The injector relay would be the computer right??? The fuel pump relay could cause that problem!!!! good luck and let me know