My 89 Camaro is running rich, leaving black soot when I run it in idle and rev the engine. I have replaces the throttle sensor, oxygen sensor, idle sensor, charcoal canister, spark plugs (which were black with soot) and wires and rotary cap, spark timing module, and knock sensor. Even after all of that it is running rougher than ever and is still running rich. Now it even wants to die when I it's in drive when I stop. I have to hold the gas pedal down a little to keep the RPMs high enough to keep it running. This started after I changed the spark plugs. any ideas?

 

Have you scanned it for codes?

Sounds like you may have a faulty coolant temp sensor, reporting too low a coolant temp, causing the ECM to run the engine in "cold start enrichment" mode.