Gary,
Check the rubber seal on the tip of your fuel injectors. On our van, I found
that air was being drawn in past the injectors when the idle was at low revs.
This caused the OXS to detect oxygen and the ECU determined that the mixture was
"too lean". The ECU enriched the mixture and the engine rev'd higher. The rubber
seals on the injectors sucked in tighter and less air was sucked in. The OXS
read less oxygen so the ECU leaned the mixture. The resulting oscillation had
about a one second interval.
The way I tested this was simple. I pressed the injector in while the engine
idle was oscillating and the oscillation changed.
The fix is also simple. The spectacle shaped metal pieces that hold the
injectors in place need to be bent (flattened) a very slight amount so that they
press more firmly on the injectors. The injector seals should also be replaced
for best results.

Gary McEachern wrote:

> I'm still having a problem with the FI in my new '87 weekender. When I first
> start the van the O2 voltage starts around 0.45V and slowly climbs for about
> 3-5 minutes till it reaches approx 0.8V. Once it exceeds +0.8V the voltage
> starts to ramp up and down from 0 to 0.8V every few seconds.

This is normal. Your OXS is working correctly

Hope this helps
-Larry
'86 Syncro Westfalia Camper
'86 Syncro CrewCab Pickup