starting problem

[birdman]

ive had a problem for about a year now that when the car gets up to temp and i shut it off and it sits longer than about 15 but less than an hour it hesitates alot when i go to start it and sometimes wont. well it did it to me again last night and it got to the point where when i was cranking it over it wasnt firing at all. i decided to unplug the map sensor (because of previous experiences i had while messing with the car) and it fired right up. turned it off, plugged it back in, re-started the car and was on my way. the map sensor is new so i dont think its going to be that, any clue what might be causing this? thanks.

[series8217]

Probably a fueling problem at low RPM / low voltage. Corroded fuel injector wiring? Weak battery? Bad ground somewhere?

[Juglenaut]

ICM coil problem, check for spark. Without testing for fuel pressure curve the fuel pump, fuel filter, or fuel regulator can cause this.
Ground Problem:
A voltmeter is needed
one probe on the battery negative and one on the engine. Do the same from battery-Frame, Battery-body.

[GremlinZ34]

Crank sensors can cause hard hot starts too. I know mine is going because i'm in a similar situation.

When the engine heats up, the plastic and metal around the sensor expands, this causes cracks and rot over time. Eventually it stops reading acurately and causes the car to have hot starts. In really bad cases the car can stall/shut off while driving... but thats the extreme end.

The sensor is just a magnet that reads when the crank goes by an tells the computer when to fire which cylinder... thats a really basic explenation but you get the idea...