Suddenly, a rough idle
 

grrr, small issues popping up...

The '90 na suddenly developed a rough hot idle. Only when hot. Starts and warms very smooth, but once up to temp, it starts to idle rough and low. Hot start is now very difficult as well. It's always had minor hot start issue but now much worse.

The issue started after I replaced the driver's side heater hose. The fuel lines had to come off, etc to get to it. Not much room down there.

What I've done so far:
-Diconnet & reconnect all spark plug lines - all good (near new condition)
-Ensure fuel lines are good - no leaks or anything
-make sure all vac lines are good - no issues
-inspect spark plugs - all have about 10k on them, look fine

What am I missing? I can't shake the feeling I must have bumped somthing while doing the heater hose.

I'm going to check the thermowax. I was hoping someone was going to jump in and give me a fix in 10min instead of me having to research for hours, but oh well :)

This all started when the famous heater hose under the oil filter blew. I was lucky enough it was a smallish crack and made a huge cloud of fog behind me, so I caught it before anything got hot. Might just be air in the thermowax line.

Check yer compression

Ive had the same problem in my 87 TII since I blew out that same heater hose 2 weeks ago. It Idles all over the place now, sometimes its perfect, but then it jumps up to 1400rpms, then a little while later it will be idleing at 600. Ive checked for vacuum leaks on the intake side, and replaced all the plugs. I dont know what else to check. Could the thermowax cause problems like this?

yeah, apparently so. The warm-up and idle system on these cars is complex. check this thread out as an example: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/