[randy78]

black soot will be excess fuel

check the TPS

clean the IAC and the hole it is threaded into in the intake

check and clean the EGR and orifice out also

02 sensor could very well be dead/faulty

injectors may have dirt in them and be stuck, or just need to be rebuilt due to age and mileage

try fuel injector cleaner fuel additive after cleaning the IAC out

i bet it is severely carboned up by now, it is simple to clean, it is threaded into the TB unit and is round and barrel shaped, one electrical connector with 2 or 3 wires- it is the idle air control valve assembly and has a spring loaded pintle on the end of it inside the TB unit- it controls idle speed mainly


fuel mixture is controlled partially by many different sensors including the TPS, ECM temp sensor, and the 02 sensor(s)

the TPS is also attached to the TB unit and is moved by the throttle shaft of the TB unit

the temp sensor will be in the therm housing or in the front area of the intake by the therm housing, there may be two of them depending on the year make model, oval shaped plug, two wires

make sure all electrical plugs are tight and clean

use electrical cleaner spray

check all wires for any breaks inside them that you cant tell, beneath the insulation, it happens sometimes and causes lots of issues often, also make sure ground wires are not broken at the crimp connectors where they are bolted to the engine or body, if the wrong one is broken then the ECM will be affected, but this is mostly the case on FWD cars and such where they are bolted to a bellhousing bolt and do cause running and idling issue commonly


check cap rotor and wires for arcing or leakage

such ignition problems are VERY common on the TBI gm engines and cause all kinds of oddities often

good luck