96 trans sport 3.4 starting issues

[mikcro1]

I have a 96 Trans Sport that has a strange starting issue. When the tempurature is between 25 and 35 the van will not start. The fuel pump relay chatters and engine cranks over great but will not start. Let the van sit for a couple hours in the sun and then it will start without any problems. I have checked and cleaned all the grounds I could find as well as added a new frame ground thinking it was needed. The van started everyday during the winter no matter how low the temp got out side. Now that it is starting to warm up I am having problems. I have checked the battery, the alternator to make the voltage was correct and system is running at 12 to 14 volts. No error codes being kicked by the computer. I suspect it might be a faulty ECM but unsure, any and all help would be great as I at wits ends with this van.