This is an aftermarket replacement idle air control (IAC) valve for your 1986-1991 Vanagon waterboxer. If you are unsure how to test your existing part to see if it's bad, read the following article:
Article: Idle Control System: 1986-91 Vanagon
YOUR ORIGINAL PART MAY JUST NEED A CLEAN: We've found that a poorly responding Original Equipment (OE) IAC valve can often be revived with some strategic cleaning. Remove the OE valve and spray some carb cleaner into the bore, then use a screwdriver to actuate the piston back and forth a few times, taking care to not scratch the sealing surface of the piston while working the cleaner into the valve. If your OE valve didn’t improve with cleaning, our aftermarket valves are a high quality replacement. Unlike some poor quality aftermarket valves we've seen, these IACs seal completely when closed and operate smoothly.
Installation note: Please keep in mind that this part may not solve your idle issue—but it certainly doesn't hurt to replace it. It is often challenging to diagnose a Vanagon running issue, because these vehicles don't have modern on-board diagnostics. If you plug in this part and it does not fix your issue, you still own the part. Click here for more information about returning electronic parts.