1985 e30 325e unexplained surging idle

I have been through the threads all over online for months now..nothing has helped. I have an erratic surging idle, the idle varies from consistent high about 1200rpm's to surging from 500 to 1200 to surging from 800 to 1800 I've noticed about four different idle patterns now. It occurs approx 90% of the time, the other ten percent it idles about 1000. I replaced most vacuum tubing (all the others are ok, atleast seem to be), replaced the intake elbow. I cleaned and tested the ICV with a 12v source and it operates, I could not find any resistance specs on the two wire set-up ICV. I replaced the coolant temp sensor also. The car sometimes bucks when driving and at certain speeds like 45mph in fifth gear I do not need to touch the throttle, the car will just keep going due to this idle issue. This has me completely stumped. Any help is very much appreciated!

If you have the 'linier' ICV they can get a dead part on the track. Check with a DMM while moving the valve over its full range.

It is the linear one with the two wire plug. DMM? Sorry probably a dumb question. And could I check resistance on it? I have no specs though :/

This seems to make sense though! It would be functioning but not correctly.

The test is to work the unit through its full range of movement while an ohm meter is connected. There should be a smooth even change in resistance. Any variation (ie a dead bit) will mean a new unit. Sorry I cannot give ohm value range but the dead bit is the give away.

Awesome! Thank you very much, hopefully this is the problem. I will reply back with my findings!

Ok, just ran the test and all along it's movement it remained a constant 8-9ohms of resistance. It averaged about 8.4 but never dropping below 8 or ranging above 9. I'm guessing that means the ICV is still good?

DMM= Digital Multi-Meter

You should have had a range of readings from full closed to full open. An unchanging reading of 8-ish ohms indicates the ICV is dead.

Alright sounds good! Does anyone know of a good place to buy these from? Everywhere I look they're about $200...little pricey

Rockauto has them for about $170. You could always get one from a wrecking yard but reliability could be questionable.