Ok so I am purchasing a car soon. It is currently not running. Well it runs but after a little bit it starts to run rough and smokes. I've been told it is most likely an ECU issue but I was curious to what you guys may think the problem is.

 

The best indication of a rotary engine's health is a compression test.

 

ROTARY COPMRESSION TEST:
Leading (bottom) plugs in, trailing (top) plugs out, EGI fuse out (to cut off fuel).
If the engine has been sitting for a while, spray some WD40 in the trailing holes on all rotor faces to free up any stuck seals & build compression.
Install the tester in a trailing hole & crank the engine at WOT.
Here is the tricky part.
Open the bleed valve on the tester just enough to see the needle bounce up & down between each face.
Observe the sets of three pressure peaks.
100's - good
90's - OK
80's - about worn out
If the peaks are all about the same, that's good.
If they are more than 10 PSI different, there's probably damage.
Then let the bleed valve close & see what the max pressure builds up to. It’s usually 15-20 PSI higher. Which is closer to what an electronic tester will show.

 

Is is possible to do a compression test with the engine out, without a tranny? Say on an engine stand or something.

 

Its been compression tested. 100 on all but one face which had 95.