Hi. I have a 94 Civic LX with the D15B motor.
Here's my issue: I had an oil change at a shop and about 2 weeks later I decided to change out my spark plugs and noticed all 4 had rings of oil in the middle so after some research I changed the valve cover gasket and the o rings. There was oil seeping around the entire top end so I figured that did it so I washed out the bay and there was another leak coming from the dizzy so I changed out the o ring on that. I've been having this weird up and down idle issue too. I cleaned the iacv, didn't work so I got a new one, still didn't work. So I moved on to the Speed sensor that goes to the bell housing which fixed my speedometer but didn't help, changed the pcv valve, changed the map since it looked a little cooked. My temp gauge wasn't working so I changed the sensor under the dizzy which fixed it but no coolant loss and the oil doesn't have the coolant milkshake. After all this the oil was full two days ago but I checked today cause the car started driving super rough and its almost completely dry. And its impossible to get the oil cap off.
the last thing to mention is that if you stand behind the car it has this sweet smell but not coolant sweet from the tailpipe. And when the idle fluctuates you can here the tailpipe pop when it goes up and you can feel it when you put your leg in front of it. No smoke other than cold start in the morning.

So that's pretty much what I've done and I'm out of ideas no leaks or any damage from under the car, oil pan and filter seem fine so I know the shop didn't screw up. No CEL.

Any ideas on what to try next?

 

Before swapping more parts, I'd start testing. Do a compression test, maybe both a wet and dry compression test. Might be piston rings. Might be head gasket. Possibly something else. You might also check for milky-tan oil under the valve cover and for exhaust gasses in the coolant (get a tester kit from an autoparts store).