Loose oil cap

[sfkjeld]

Had my oil changed 2 weeks ago at a local generic car repair shop. First time I’ve used them. Have noticed the idle running rough recently and have had a few coolant issues as well. Belching coolant despite no sign of overheating.

I believe I just found the source for the rough idle. The oil cap was loose. The shop didn’t seat it. I tightened it while the engine was running. The idle immediately smoothed out. Didn’t realize how bad it had become. Does this sound right? Does The oil system need to be air tight? Since I hear some air passing thru the oil filler with the car running, does this indicate compression leakage? Anyway the loose cap could cause coolant issues?