'84 240 DL w/B23 Engine not runing well with new Air mass meter
 

I will try to explain as much as I can as to what is going on. I have a 1984 Volvo Wagon 240 DL with 270,000 miles on it. I know its got quite a few miles but I have taken care of it as best as I can. Recently the engine was not running well, stuttering, hesitating, choking etc...so I went to a Wrecking yard and found a slightly used Air Mass Meter and put it in. The car runs like new, it accelerates evenly and has lots of power, but the only problem is that it it idles very rough even tho I have set it to the correct point. It also make the fuel mixture very very rich. It belches out thick black smoke that is laden with black soot, and I can almost see the fuel guage go down as I drive. I was wondering if anyone has had this problem or somthing similar, could they please let me know how they fixed it or at least made it better. THX. The only thing I can think of as to why this is happening is that, the new Air Mass Meter is sending correct information to the ECU but the ECU isnt calculating it right or something else so used to reciveing info from the old Air Mass Meter the new info confuses it somehow.

RE: '84 240 DL w/B23 Engine not runing well with new Air mass meter
 

do both air mass meters have the same # on them? I am not sure but from reading your post you are having the same problem that you had before you swapped them. Check your coolant temperature sensor for the ecm (not the gage) if there is a bad connection or the sensor is bad they can make the car run rich.