weird idle problem when warm

[hugh jass]

I'm running an obd1 s52 in my 90 e30 and once in a while when the car is warm and idling the idle will momentarily drop and then rebound. today it did it and the car ran rough for a few seconds and then returned to normal. is some electrical device kicking on causing the idle to drop? any ideas? i searched and didn't find anything that really helped.

more info:

icv is brand new
purge valve is hooked up
all vacuum lines are connected

could this have something to do with the O2 sensor heater?

[e30s52]

i have been trying to figure this out to. my e34 m50 does the same thing. it just falls flat on its face for like 2 seconds then is normal