Volvo: Volvo running rough, blue smoke., mass air meter, volvo 240 dl

Question
QUESTION: I have an 89 Volvo 240 DL.  It's been running rough for a few weeks and just the other day the check engine light came on and started running worse.  Now it's blowing blue/black smoke and smells like gas.  It's burning gas quicker as well.  Any idea what this could be?
ANSWER: Scott,
Read the codes and see what the failure is. Fuel pressure regulator, Mass air meter, vacuum leaks in manifold or tube to the throttle housing, injection control unit to mention a few.

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QUESTION: Thanks for the reply.  Not sure how to read the codes.  I just replaced the mass air meter a month ago.  I don't think it's that because it was running fine and the symptoms are different from when that failed.  I also have what sounds like an exhaust noise, like a rattle.  So I was wondering if it could be someting to do with that.  

Answer
Scott,
Exhaust leak, mainflod gaskets, headpipe gasket, failed pipe, or muffler. Rattle maybe the shield over the head pipe are loose, internal rattle the cat converter broke apart inside. If the cat has come apart internally it could stop the exhaust flow and limit the power. Don't over look the fuel pressure for problems in the pressure regulator. Like over pressureing and forcing more fuel into the cylinders, running rich with black smoke form the tail pipe.

Connect the selector lead to output 2 (MFI LH 2.4/LH 3.1) of the DLC.
Ignition on.
CB2
Diagnostic test mode (DTM) 1
Press the button once (for about 1 second).
Read off the LED flashes.

If code 1-1-1 is obtained :
There are no DTCs stored.

Continue with DTCs DI EZ 116 K CB4.

If another code is obtained :
Make a note of the DTC
Read off as before until the first code returns.
Make a note of all DTCs.