So i just bought my first rotary a couple weeks ago, a 1990 NA Vert with 206k miles on it. The motor had been rebuild sometime recently or so im told. I put a clutch in her and got her driving after getting it unstuck from reverse. Ive put about 30 miles on the clutch but ive run into a problem. I can start it up when its cold and the idle surges to do the whole fast warm up thing and it all sounds good until it gets to operating temperature. Once it is warmed up the idle bounces from about 300-900 rpms. When i drive it runs fine in gear and pulls and feels good for about the first five minutes but then ill put the clutch in too long or put it in neutral to where it is just idling and it will stall. I believe it is a vacuum leak but i am not sure. I have tested and cleaned the iac valve, replaced the brake booster rubber vaccum lines, and taken the upper intake off to look for disconnected hoses. The one thing i have found is when i spray brake clean in the passenger corner of the engine by the left fuel injector and iac and the five metal vaccum lines, the idle evens out and sounds way better. If anyone has any tips or helpful advice for me i would appreciate it very much. Also i should add it is 100% bone stock.

 

I also noticed when i am driving if i put the clutch in the check engine light comes on and if i let off the gas in gear the check engine light kind of studders and flashes on and off but its never on when im parked not moving.

 

So ive replaced the seals on the socondary fuel injectors and nothing changed yet. Also when reading through my original post i noticed i put iac valve i ment to say bac valve.

 

Definitely sounds like you're on the right track with a vacuum leak. Keep testing for one. If you don't have a way to smoke test it, you can do what I do and fill the engine with compressed air instead. I bought a cheap PVC cap and drilled a hole to thread an air hose coupler into the end. I can put 20psi into it and feel around until I find the leak.

 

Can you explain where you attach the PVC cap? I too am having s vacuum leak issue and spraying break cleaner around, I get no change.. I have replaced majority of the vacuum hoses, but getting a similar issue to what Mazdadud describes... check engine light, goes away with acceleration, etc.

 

I used a vape to blow smoke into the intake tubes through the air pump and such and found a few leaks. The major one was at the hose that goes from the air box to the air pump. theres a little elbow that screws on and it was leaking arounf the side put some rtv on and its better.