'87 4kq running poorly

[Andrew Buc]

I should say first off that I'm almost certainly going to take the  
car into the shop in the next day or two rather than try to fix it  
myself. But given my commute, being without the car will be very  
inconvenient, and I'd like to get an idea of how much downtime and  
expense I'm likely to be in for.

This all began this morning on the commute. Sometimes the car would  
lose speed for a few seconds, then abruptly speed back up. It got  
worse on the afternoon commute. I drove around a bit after getting  
home, and the problem has leveled off, but at a very inconvenient  
level. Other symptoms:

The car starts fine and idles fine very briefly, then the idle  
becomes slow and rough, but it does keep running. It doesn't run very  
well on light throttle--I have to really mash it to get going from a  
standstill. Under way, I often find myself using a lower gear and  
more revs than I normally would. The temporary slowdowns followed by  
abrupt speedups have continued.

Any insights? Thank you.