Oldsmobile/Buick Repair: 1991 oldsmobile cutlas supreme, oldsmobile cutlas supreme, coolant temp

Question
I have a 91 cutlas with a 3.1.Out of nowhere the service engine soon light comes on and it sputters and throws black smoke.I replaced egr valve,speed sensor,manifold air temp sensor,and its the same. I HAVE A COMPUTER KEY AND REPLACED THE STUFF AND NOW I GET A CODE 43,it means contact is not right somewhere right?ecm. you said in another answer it could be a temp sensor in the fuel injection system. I am lost please help.

Answer
Coolant temp sensor.
http://www.chevytalk.org/threads/showthreaded.php?Cat=0&Number=1366279

Computer key?

If you mean you read the codes, and got something like an oxygen sensor code, that doesn't mean the oxygen sensor is bad....it could be giving a correct reading, and the problem is elsewhere. Like a rich oxygen sensor reading could be leaky injectors. A lean reading could be a vacuum leak. Etc.

Van