We have a 1993 Chevy C1500 with a 5.7 that is dumping fuel at idle. We've put new injectors in it, new map sensor, O2 sensor, air control sensor, temp. sensor, new computer & chip, EGR sensor, Pickup in distributer, new distributer wires, new cam, lifters, timing chain & gears, fuel pump,& top end of throttle body. We've taken it to Sands Chevrolet & Gateway Chevrolet and nobody can find the problem. New crate motor from dealership has only 85,000 miles on it and transmission.

Idle air control valve or passages clogged partly . Your best bet , take it to a qualified repair shop.

The first thing you have not checked is fuel pressure.
The pressure could be low, or the fuel filter could be clogged.
It takes more fuel to run the engine in the first 5 minutes until it warms up than under normal conditions.
The codes mean the sensors are not giving the computer the readings they should, but it does not always mean the sensors are faulty.
If the engine is running rough, or the fuel mixture is lean, the sensors will show that.
Code 44 is O2 sensor reading lean which may be true.
Code 33 is MAP sensor reading low vac which may also be true.
Another possible cause is the coolant temp sensor may not be telling the computer the right thing. If it tells the computer the coolant is 200 degrees and the engine is cold, you won't get enough fuel thru the injectors.

Have you checked fuel pressure? Maybe the fuel pump or fuel filter is not providing enough pressure at the fuel rail for the injectors to work.
Also, clean the mass air flow sensor with a sensor- safe cleaner.
Good luck.

symtom of faulty I A C motor (idle air control motor) this regulates the idle air to fuel ratio when at idle, when faulty dumps more fuel ,then the o2 sensors tell computor to much fuel for throttle position/ speed so computor backs off fuel almost stalls dumps fuel again and repeats. we call this hunting. because air/ fuel mixture changes idle goes up n down.
im sure the dealer will gladly relieve you of lots of money.....try aftermarket or an auto wrecker may have one . careful i've seen some volvo engine parts need programing after instalation (dealer only)!!!

sounds like it needs a good tune up and new airfilter will sort it out

oxygen sensors
map sensor
mass air flow sensor
fuel pressure regulator
idle air control valve
throttle postion sensor
fuel injectors
egr valve
All these sensors send a signal to the ecm to regulate the air/fuel mixture.

I'd check the MAP (manifold absolute pressure)sensor.

were the injectors replace? 4.3l engines are know for messed up distributors

check to see if one of the injectors is pouring more gas than the other while idiling. if one of them is check the wires going to it to see if there is a short. if not the injector is probably junk.

relace the throtle air idle valve.The temp switch will allso cause this problem.