Describe your Specs timing Gmc 350 1988 Problem. The engine keep flooding. I have back fire coming back through the throttle body and the exhaust. I also need to know the timing. I rebuilt the thottle body now they are pulsing right right

Can you start it with starting fluid instead of fuel from the injectors ?
Any trouble codes in the engine computer ?

https://postimg.org/image/ed118sfxx/

Click on the link.
Hope you can read it, I tried to get everything in one picture. Have you set the idle? The info is for setting the idle. I can give you the specs, but, I need engine size, also, is this automatic or manual tranny? Check fuel pressure if you haven't already, 9--13 psi, throttle body fuel injection.
How long since over-all tune-up? You can use digital multimeter to check throttle position sensor. Probe the dark blue wire at sensor connector, key on, no need to start it, then move throttle lever under the hood by hand, the voltage should move up and down smoothly. Closed throttle about .5v fully open about 4.5v.
There could be other issues?
As far as factory idle specs, if this is a high-mileage engine, those specs may not work very good?

have you checked the needles or floats in the carb?

What kind of vehicle/engine is it? this question is very vague. Your injector will be on the intake manifold in a direct port fuel system and there will be multiple injectors. You may have fixed one, but you may have more to clean/replace. If it's a throttle body system, the problem is not your injection anymore, but your timing (distributor or cam timing) or you could have bad plugs. There is no reason for fuel to be coming to the exhaust, but the products of combustion of unleaded fuel are CO2 and water. If your timing is off, or rinning high rpms, then, perhaps fuel will get into the exhaust, but that again comes back to throttle and timing. And your catalytic converter on your vehicle should clarify this.

The throttle body needs to be cleaned, When you disconnected the battery, the computer reset to factory defaults and now with a dirty throttle body, it will run poorly at idle. Make sure both the front side and rear side of the throttle body are cleaned thoroughly.

your timeng is off this can only be reset by a computer as the computer controls is and from time to time thay do go off.

The 3.1 engine does not have a belt,it is a chain motor.You do not need to remove timing chain to remove head.

Possibly a busted fuel pressure regulator diaphragm. The regulator is mounted to the end of the fuel rail.
With the engine idling, pull the vacuum line off the regulator port. If gas comes out of the port, replace the regulator.

Sounds like you have an injector leaking. Have someone just cycle the key on and off to run the fuel pump but don't crank the engine. If you see fuel dripping from the injectors, unbolt the injector cover on the throttle body, remove the injectors and replace the orings around the injectors.

I lost you in chat and I can tell you that you need to clean the throttle body and set the choke on the throttle body, if it is carburated then you need to replace the float as it is allowing to much fuel into the system and flooding the engine the reason you are told to put your foot down all the wa is that is for clearing flooded engines. please contact me so I can help my e-mail is [email protected] and our programs did not wantto talk to each other. Avid101