why does my 85 vanagon want to stall without the a/c fan on,,even though the a/c isn't working optimally?

I think the idle should be set fairly high on these vehicles between 800-900 rpms if memory serves... There ought to be an adjustment screw on the throttle body my guess is the idle is low and/or the vehicle needs to be tuned up...plugs,wires,filters, timing timing is 4-6 degrees ATDC if memory serves... If it was a problem with the FI system then it ought to have trouble idleing even if the AC were engaged, but I think it's running stable because the car increases the idle when the AC engages to prevent stalling. So I'm almost positive that all you need to do is adjust the idle. A repair guide ought to have more information. Jeeze I haven't said 'ought' that many times all year.

The idle adjustment screw is NOT on the throttle like on many other autos. It is the large plug in the throttle body that can be turned with a flat screwdriver. There is a switch that increases idle when air con. is turned on to compensate for the load placed on the engine by the air con. compressor. The idle speed probably needs to be adjusted with the air cond. off.