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
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.
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 the best replacement we’ve found. These aftermarket valves operate smoothly and accurately, but we've noted that their pistons do not seal as completely as the pistons on the OE valves. In most cases this incomplete seal doesn't affect performance, but we've seen a few instances where this metered, leaking air can cause a high idle. We do not recommend these valves for use with our Engine Management System, which uses less air through the IAC at idle and is more sensitive to a leaking valve.
HAVE A HIGH IDLE? It is simple to test whether our aftermarket IAC valve is the cause of a high idle. While idling with the IAC unplugged, pinch the air hose leading to the IAC inlet. If pinching this hose drops the idle to a lower than normal speed, the air leaking through the IAC may be causing your high idle. If the high idle won't continue with the IAC unplugged, or if pinching the hose doesn't eliminate the high idle, the IAC is not causing your problem.