91 s10 with 4.3 very hard starting cold or hot,if i give it a squirt of fuel down the throttle body it starts right away.Have replace fuel filter,fuel pump,and plugs.

the iac sensor is along the side of throttle body , did you give the throttle plate area a good cleaning out this is where the air path is for the IAC sensor , a lot of idle problems have been fixed with a can of throttle body cleaner and few good squirts of the stuff down the hole

I assume it starts and runs fine when cold? It could be a faulty TPS. Since the TPS adjust the setting of the throttle (butterfly plate) inside the throttle body. If the throttle body is dirty it will give you satarting/running problems. Make sure its nice and clean. Then see what happens. If problem persists after cleaning I would suspect the TPS is bad.

Vehicles need fuel, spark, and air to run. You started with the basics like spark and fuel, great. Slow down on the parts installations and take yourself back to basics.

1. Check your fuel lines for leaks.
2. Inspect the vacuum lines for cracks ( you stated it got cold outside. This may contribute to old hard lines cracking).
3. Remove the air filter box and filter and make sure airflow is free of any blockage. Test car without air filter installed and see if it stays running while giving gas. If it does replace air filter
4. Check the throttle body Mass Air Flow Sensor. This detects how much air is coming into the system. It reports to the main computer. If the MAF tells the computer there is significantly not enough air the the system will shut down. My guess would be a big vacuum leak or you have a bad MAF.

Check the cable to the temp sender unit is attached if so check the unit is working with a ohms meter. check the throttle cable is not binding ,the throttle leaver stop at the throttle body housing should be fully closed .

What is 3.4.

First 2 things to check are the choke adjustment and operation, and the raw fuel squirt from accelerator pump when throttle pumped. You should be able to see a good squirt of gas into throat of carburetor when you move throttle linkage to wide open quickly. Choke plate ( butterfly) should be in closed position for cold start, then open gradually as engine warms up. Have you checked that as of yet? With re-start problems after warm up, may be needle and seat assembly needs replacing to retain proper fuel level in bowl for starting. If they are dirty or worn, fuel in bowl runs back out. It sounds like a carb rebuild kit might be a good idea.

did replace with the recommed plugs -hot or cold plugs

The usual cause for this problem is the IAC valve. It gets carbon buildup on it that becomes sticky when it is hot, such as after reaching normal operating temperature.

Carefully remove the valve from the throttle body, paying close attention to where the rubber o-ring is...it may come out with the valve or it may stay seated to the valve mounting hole. Either way...don't lose it.

On the valve is the pintle that sits in the throttle body air path, allowing or restricting air intake when your foot is off the pedal...if it is stuck, then pushing the pedal is the only other way your engine can get air.
Use a tooth brush and brake cleaner or throttle body cleaner on the IAC valve and inside it's mounting hole. Carbon buildup in this area is completely normal, however, running premium fuel and keeping a clean air filter will help the engine keep the right air to fuel mixture and minimize the problem...and save your starter too.

Start with the simple and replace your fuel filter, a dirty filter can cause your engine from starting. At worst, your fuel pump has failed and will need to be replaced. Before replacing the fuel pump, inspect all the fuses and wire leads from the fuel pump harness. Note: that the ground wire is separately grounded at the frame, so inspect that for any damage due to corrosion.

You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors. I think each injector is on a seperate driver on that one. Check for pulse to all of them.

You may be weak on fuel pressure, even a couple of lbs low on a cold start will cause a no start. Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. One test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test, here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure. Later V6 and V8 gm engines should have 60-66 fuel pressure.
* Cold start should be 64-65 lbs of pressure. If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
* Engine running should be 60-66 lbs pressure depending on engine load.
* Full pressure with return pinched off should be 75-85 or more. and if it has a fast leak down after shut off you have a leak.

The 75-85 is only a check on the capable full pressure of fuel pump. If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.

You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors.

You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start. Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. One test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem. Run the full fuel pressure test and post back pressures. Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.

Also you mentioned that you replaced the fuel pump, it's common for the $15.00 wire harness from the fuel pump to the frame will break and there is a bad connection till the wires heat up. You can try this trick, turn your ignition on for 30 seconds "engine not running" and then turn it off for for 5 seconds and then try to start. This will energize the fuel line if the fuel line check valve is bad which is a part of the fuel pump and will heat up the wire harness which will make a better connection and see if the engine starts easier. Regardless, inspect the wire harness for corrosion and the ground is good. Good luck and keep me posted.