Where is the modulator valve located on a 1987 Ford Taurus engine?

The 1987 Ford Taurus didn't use a "modulator valve" in the same way some later vehicles with electronic transmissions did. That terminology is more associated with later automatic transmission systems controlling shift firmness.

The 1987 Taurus likely used a simpler system. Instead of a modulator valve, the shift pressure was controlled by the governor and a pressure regulator inside the transmission itself. There's no single externally accessible "modulator valve" to locate.

If you're having transmission problems, the issue lies within the transmission itself (worn components, low fluid, etc.) and requires a professional inspection. Describing the specific transmission problem you're encountering would be helpful in getting more targeted advice.