When the weather is hot, car will shut down.

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7/09/2010. I have this car with approximately 162,000 miles and have had good reliability with the car. I've replaced the oxygen sensor 3 times that was still under warranty because I bought a new one for it at 146m miles. I've replaced the MAP sensor. Now, when it gets hot, the car will shut down, then after a cooling period and taking the + battery cable loose, I can get the car going again, for awhile, then it starts in again. I've taken it to a Chrysler Dealership & they have lost their diagnostic chip, for my year car. They then suggested a guy that used to work for them to check into it. I got these codes: 12;21;51 & 55 before I replaced the MAP sensor. Now, afterward replacing the MAP,I'm just getting the code 55 on the computer code readout. It still shuts down! I need help in diagnosing this. Now head gasket was replaced about 40000 miles ago. The timing belt at the same time...even replaced the fuel filter, even the fuel pump in the gas tank was replaced. Any ideas? 7/10/2010 I went and filled it up then drove 107 miles, then the oil light flickered and then it died on me! Help anyone? 7/22/2010 I'm replacing the fuel pump in the car. Thus far it hasn't shut down again, but I haven't been anywhere yet either...with no response here, I'm throwing 'parts' at it now.... nothing else to do here with some type of clues.. 08/01/10 So far so good...no long distance trips yet...