I have the same problem with my 87' Syncro Westy, 83,000 mi. It has become so bad when it does happen that it is not drive able. If I turn off the ignition and compression start it, it will go away for a few
minuets and then start acting up again until it disappears. It also does it after warming up at idle (approx. 5 min.) and even with the O2 sensor unpluged. I have decided it is either the ECU or the airbox
but it never seems to do it when I have the tools in my hand. Check the normal things: temp sensor, O2 sensor, injectors, fuel pressure. I will let you know what I find out.

Dana E Hager

Nazareth, PA