Would this also be the culprit in my 85? When I’m park (but not drive) the idle increases to about 1500 then drops back down to 900. Repeats until I put the van in gear but if I take my foot off the brake it will accelerate to 1500 then drop to 900 again. I have a 2.1 Boston Bob in there with about 75,000 km. 

Thanks
Jeff

Sent from my iPhone

> On Jul 9, 2021, at 6:41 PM, kenneth wilford (Van-Again) <kenwilfy@comcast.net> wrote:
> 
> The idle stabilizer control unit behind the rear tail light controls this
> along with the idle air valve on the top of the engine.  I would start by
> checking your throttle position switch to be sure that it is clicking and
> functioning at idle.  If that is working then it is either a problem with
> your idle control unit or the IC valve.  Usually the unit is the bad one,
> and we have rebuilt and tested units available.  If the idle control unit
> is good (only way to test is to install it in another vanagon and see if it
> works)., then you could get a new ISCV.  The best way to test things if
> your switch is fine is to get a friend with an 87-91 Vanagon and swap your
> stuff with his and see if the problem follows the parts.  There really
> isn't a good way to test beside this in my opinion.  There is a test that
> the idle valve is supposed to vibrate when the key is on, but I have found
> that this test doesn't really tell you anything.  I have had vans that
> idled fine but didn't pass the idle valve vibration test.  I hate to just
> throw parts at a problem, but if I had to guess the problem I would guess
> the ISCU as they go bad a lot.
> 
> Ken
> 
>> On Fri, Jul 9, 2021 at 7:02 PM Ryan Cresawn <jrcresawn@gmail.com> wrote:
>> 
>> On July 6, 2020 I hired a shop to fix my factory AC in my '91 Vanagon
>> camper with 2.1l engine. The old compressor was leaking and the shop
>> replaced it. At 11.5 months into a 12 month warranty the AC wasn't cooling
>> well. I returned to the shop last week. They identified a refrigerant leak
>> in the compressor and replaced it under warranty. I picked up the Vanagon
>> yesterday and was told that I need to hire a shop to fix the low idle when
>> the compressor is on.
>> 
>> I drove the Vanagon home and confirmed that when the compressor was running
>> the idle speed of the engine would drop from around 900-950 to about
>> 600-650. The engine did not stall but it felt like it was close to
>> stalling. How should I begin to troubleshoot this issue?
>> 
>> Thanks in advance,
>> Ryan
>> 
> 
> 
> --
> Thanks,
> Ken Wilford
> John 3:16
> www.vanagain.com