My Civic DX just had its idle air control valve cleaned out well - it was gunked up, and would shut off when I try to idle. I would feel a slight shutter, and then things shut off.

I got my car back from the shop last night, and today I drove it nearly 100 miles with no issues (that was one hell of a test drive). But, I have two questions.

First off - when I idle, I still feel that slight shutter at times, but the car doesn't shut off. You can tell the motor either quiets/strains/etc after the shutter, but things pick up and the car functions as normal. Is this normal for a Civic when idling? I am wondering if the shutter was actually the IACV opening, but since it was clogged no air could get through, and therefore it would shut off. Am I on the right track here, or does something need to be adjusted?

Also, when I drive and hit around 30-40 mph, the car shakes a bit. Not much, and the car runs fine, but I typically give it more gas or slow down a bit to take it out of that gear (automatic, but I can feel it shift). Is there a reason why it may be doing this?

Thank you all for your help!