starts and immediately stops
 

I have a 2003 sonata 2.4 base model when it sits out in the sun all day at work it starts and immediately stalls for about 6 or 7 times in a row before it decides to stay running. Since I bought the car last fall I noticed it had some aftermarket theft module wired in under the dash that I had no fob for so I took that out hoping to solve this problem but its still doing it sometimes. I will add that when at home and the car isn't in full sun it doesn't do it. I will also add I live in phoenix so yes its a scorcher right now.

Got to look at what is starting and then immediately stopping
Is it spark, fuel pressure, injector pulse??
Is the fuel pressure regulator or pump not holding pressure?

Not in rust belt means the vehicle should be a lot easier to work on.

Can you try this,
When you are ready to start the engine after a period of heat, turn the key on, but do not attempt to start the engine,then turn it off. do this maybe 4 or 5 times then go to start it .
Does it still have the same problem?

Sounds like the fuel pump is going out. In their death throws they will start and stop for no rime or reason. In my mind the pump is talking to you so u might want to listen otherwise u might find ur self on the side of the road with your wife yelling at you. While at home turn on the key and leave it on but do not start the car. Go under the car r open the trunk and listen for the fuel pump humming. If u hear it but it's sporadic then that's the culprit. And by the way if it is the pump take it from me and buy a quality one! Good luck

Well, another cause could be a clogged exhaust system.
But, it is best not to guess.
Better to go test it.
Don't just throw parts at it