My 1992 no-seq turbo fd3s when it is cold start .its idle is so rough
but after drive it around 5-10mins back to normal
anyone knows wt happening ?

 

could be the air sensor. rotary cars need to be warm before you drive. rotaries run high rpm when you start them to make the car warm. id recommend letting it warm up for like 5 minutes before you drive and it should be good to go. if not check the bypass air sensor.

 

100% true. I had the same problem when I first bought my car and asked the same question. Ever since then, I let it warm up about 2 minutes before I even leave the parking lot and it runs perfectly fine. Usually it should take those 2 minutes for the temp needle to reach the middle of the gauge, at that time it is warmed up and ready to roll.

 

Yep...
I actually warm it up then go but I check probably one air temp senor that isnt function so well

 

Definitely needs warmed up. I believe that's why Mazda engineered the ECU to run the car at something like 2500 RPM for a couple minutes on startup (stock ECU, not positive which model years). I usually let my water temp hit about 60 deg Celcius before expecting it to perform as desired. At that point the tach needle is as still as can be at idle.

If you don't have a digital water temp meter, I would imagine that 60 deg C would probably be just shy of halfway up the stock meter.

 

The high-rev is just the cold start system. It should be warmed up at idle for 2 -5 minutes before driving to reach operating temperature/ wait for the thermostat to open.

If you're worried I'd check all the fluids, test for spark and compression to put your mind at ease.