I also have an 87 190E-16V. The cold start valve is located between the 2nd and 3rd intake runners, on the throttle-body side of the idle valve / junction. You'll see what I mean. It's easy to change, but I'd check to see if the correct Voltage/Current is arriving at the cold start valve before you buy a new one. Sorry, but I'm not sure what the correct values are supposed to be. You might want to buy the service CD-ROM as it has lots of cool info, including a complete troubleshooting guide for the fuel management system.
Hope this helps,
87 190E-16V Blk/Blk 5Spd.