like" mallen ", i worked a total of over 38 yrs in mil and goverment defence radar/sat electronics , be very carfull applying heat as if too much the main intergrated circuit will be gone in no time , i would let it run with ecu cover off until it goes bad then spray freon or circuit cooler on it , just a quick spray may find it , i would agree electrolic caps go bad over time but not intermittent too much , they go bad they stay bad.
i would suspect a ic as many time they are heat sinked to the chassic and over time the heat sinking paste goes away, it would be very hard to remove the main ic as it more than likley has 32-48 pins soldered down , also no replacement part number , where as a cap would be marked with the size and could be replaced, like mallen said with temp changes the printed tracks on the board and the parts soldered to them do stress and could open up.
i would be very carefull and not apply heat to a intergrated circuit , also
try and find a spare ecu , it must be for the exact model and year /transmission you have.
