You need to test it when the problem is happening. Fuel pressure should be checked and spark should be checked for a start. Something is going to be out of spec and give a clue.
There may be a case of a coolant temp sensor that is giving bad data to the PCM causing too rich of a condition.
Checking for codes in the history may be helpful.
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Thursday, March 20th, 2008 AT 6:07 PM