Cadillac Repair: HELP, fleetwood brougham, coolant leak

Question
QUESTION: Good Morning, i was wondering if you can explain to me what my propblem is with this vehicle.  i have a 92 fleetwood brougham RWD cadillac and just the other day my check engine light came on and it would cut off while i was at the light or stop sign. i went to get a oil change and i put some fuel cleaner in the tank and all of a sudden the drivers side of the engine smokes awfully and black smoke comes out the exhaust. also, recently i discovered that my coolant is leaking awfully and i am unsure if its the heater core or possibly the water pump. please help me out with this matter.  

v/r
Sailor in NEED of answers

ANSWER: Roderick,
Find and fix the coolant leak first. Don't want to overheat! As for the rest, first check for On-Board Diagnostic codes and then let me know what you find.

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QUESTION: HOW DO I FIND THESE CODES THAT U ARE TALKING ABOUT???

ANSWER: Roderick,
The "codes" I was referring to are actually called DTC's, or Diagnostic Trouble Codes. Your car has an On-Board Diagnostic system, OBD for short. It monitors several systems in your car and reports (via the "check engine" or "service engine soon" light), and records information concerning faults that occur with the monitored systems.
If you are a DIY kind of guy, we can proceed with diagnosing but if you are not, I'd suggest simply taking the car to a shop. Places like Auto Zone etc. will check your codes for free. At that point, you can get back to me with them, and we can go over them. If you'd prefer, I can tell you how to access them yourself, and then we can go over them. Your choice.

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QUESTION: THANKS SIR.  ID PREFER IF U COULD GIVE THEM TO ME SO THAT I DONT RUNTHE RISK OF SOMETHING MAJOR HAPPENING TO IT.

Answer
Roderick,
To enter diagnostics:
Press the "OFF" and "WARMER" ECC buttons simultaneously until the bulb segment check begins (all the digits light up). The system will list any DTC's logged, first current ones, then history ones. Then it will return to "00". At that point, you can clear the DTC's by pressing "OFF" and "LO". After that press "AUTO" to exit the system. Write the DTC's displayed and either look them up online, or contact me and I'll go over them with you.