Car starts hard when engine is cold it back fire or acts like it is flooding but starts good when engine is warm

no car told maker or model or engine size.
there are lots causes that, hard starts
if spark good and strong and even HV spark wire sets fresh.
the short list.

1. bad fuel
2. too much fuel cranked and floods
3. IAC bad, idle air valve stuck and wants to flood cold.
4. cold idle is the big clue, where too low. IAC failing
5. EGR sticking open at idle. possible.
6. if you press gas Pedal, at 5% (about) and starts easy and likes that until it worms up that means the IAC is dead.
7. I stop here lots more, no car told.

all cars modern EFI is it EFI> have IAC and ISC valves 1 or both.
and if stuck idle fails. hot or cold.
no car told why post like that 100 year of cars and 10,000 engines.
????

Think about how the vehicle is acting. Starts fine when cold, hard to start when warm. In these computer operated systems, the computer runs everything. Starts fine when cold: the computer has the engine in cold start mode putting more fuel in till it warms up. Temperature sending unit in the manifold sends a message to the computer telling it to stop the cold start mode and it stops dumping excess fuel into the cylinders and it runs fine. IF, mind you, IF the temperature sending unit is faulty, it's not telling the computer to stop the cold start mode and is flooding the engine with fuel cause it's sill in cold start mode. This is my take away on your situation and the temp sending unit is something to check to be sure it's functional. Check it out. I hope this WAS the answer to your problem my friend. It's typical. Luck to'ya Bro.

May just be a bad temperature sending unit. Once warmed up, it's supposed to go off cold start, which puts more fuel to the engine. If sending unit is not telling the computer the engine is warm, it will still be putting more fuel into the engine and flooding it, making it hard to start. Check/replace said sending unit and you're good.

It sounds like you have a "flooding" problem, where you are getting too much fuel on the warm start. It takes more fuel to start a cold engine than a warm one. By holding the pedal the pedal to the floor, you are telling the computer to do a "clear flood" operation, and that lets you start the car. The culprit is probably the Coolant Temperature Sensor. If this is faulty, it will tell the computer that that the coolant (thus the engine) is much cooler than it really is. This results in the engine flooding when warm. It may also run rough at idle after warm start since it is still getting too much fuel. You will also notice a massive loss of fuel economy. Replace the coolant temperature sensor.

Have a test done on the glo-plug system as it appears that they have burnt out and are not pre-heating the cylinders or providing a source of ignition for the atomised fuel from the injectors

Could be several things.
If the ignition module on the side of the distributor is failing, it can cause the plugs to fire at the wrong times.
If the distributor cap is faulty it can do the same thing.
If one of the injectors is leaking, it can fill one of the cylinders with fuel when you shut the engine off. It would act like the engine is flooded when you try to start it.

Sounds like either it has a bad valve, or worn rings. With the mileage, I would suspect it's just plain getting worn out, when the engine warms up it internal tolerances are better then cold.

do u mean hard to turn over or fire engine

Check fuel pressure, and regulator. A leaking regulator gives a warm engine more fuel [ it does not like it] a cold motor does. same as a flooded motor. Good luck

Engine temp sensor could be faulty not letting enough fuel be commanded by the ECM .