Gregg, as Dennis says, when the van is running poorly, try turning the
ignition off and then back on again.  If the van runs better for a
minute then starts messing up again it is definitely an oxygen sensor
problem or an oxygen sensor circuit problem.  Let us know what you find out.

Ken Wilford
John 3:16
www.vanagain.com

On 5/17/2012 5:05 PM, Gregg Carlen wrote:
> Hi all,
>
> My 1990 Westy (automatic, 2WD) has been running great since I had the heads
> redone, tune up, coolant replaced, exhaust repaired, etc, this spring. Last
> summer, I had the AC repaired (new hoses, dryer, compressor and condensor)
> and things worked great last Fall.
>
> Now that the weather is getting warmer here in Northern Virignia, I'm
> finding my need (desire) to use the AC more often. So, I started using it
> about 2 weeks ago and whenever it runs for about 30 seconds, then the
> engine seems to 'bog down' and power is lost. To explain that a little
> better, when I'm driving and this occurs, I can maintain speed for a couple
> minutes, then I loose power (almost as if fuel was being starved) and the
> van starts to slow down. If I push on the accelorator more, the engine
> continues to decrease power but is trying harder and the faintest black
> smoke starts to come out of the exhaust. As soon as I turn the AC off,
> everything resumes to normal in about 2 seconds (power, speed can be
> increased, no black smoke). Another symptom is if I am stopped a traffic
> light (or for any other reason) with the AC on, the engine will stutter and
> reduce the idle RPMs until it stalls out.
>
> There have been a few occasions where this 'AC reduces power' symptom
> didn't occur and everything worked fine. It seems like only the last 2
> weeks has this started to act up (again, keep in mind I only started using
> the AC this spring in the past 2 weeks).
>
> A few other factors that 'may' be related and influence what is occuring.
> FYI, I've had the van for about a year, so only last fall did I use the AC
> (and didn't experience any issues). The AC will ONLY turn on (AC compressor
> clutch kicks in, fan blows cold air) when the two AC switches (fan speed
> and thermostat switch) are turned up to their highest settings. If either
> is turned to a lower setting, the AC does not operate.  Also, the PO had
> removed the stock radiator fan and replaced it with an aftermarket that is
> controlled by a manual toggle switch (attached to the steering column).
> This 'AC reduces power' symptom seems to occur regardless if the radiator
> fan is turned on or off. I also have a flashing coolant light, but this van
> has always had that problem (I need to search the archives to refresh my
> memory about the cuases for that and fix that, too).
>
> I saw an archived thread about an AC idle stabilizer, but that was for a
> 1.9l. Does that exist on the 2.1? Given the symptoms above, could that
> component be causing this if its failing?
>
> Any suggestions of where to start troubleshooting/testing?
>
> Gregg
> 90 Westy (Blueberry)
>