Hey everyone, my name is Harrison! I've had my 93 miata for a few months now and have spent a good 3 grand replacing the radiator, rack and pinion, the front tie rods, the soft top, the front left fender, and the passenger mirror. Now it seems I am going to have to invest a bit more money into her. She has about 198,000 miles on her and I believe it is still the original engine. Today after getting out of class, I started her up, first she idled really roughly going from near stalling to idling at 1500 rpms and going up and down through that range. Sadly I have absolutely no maintenance info on her from before I owned her, so it could be anything. I've been trying to research common problems with the NA models, but nothing has appeared as an AH-HA! moment. Anyone have this problem with their miata? I'm going to inspect and likely replace the spark plugs just to be safe.

 

Vacuum leak check is a good start.

 

thank you, I just dropped her off at the shop and made sure to mention your insight. she was also belching out black smoke, so getting that looked over as well.

 

You should check all the belts and hoses to avid some untimely surprises on the road.

 

https://www.youtube.com/watch?v=inLP...ature=youtu.be
a video of the high idle, then taking off in first gear with a near stall, which is what usually happens. the grinding is the transmission, going to get it looked over as well, but this idle is much more pressing in my eyes. I hope it's as simple as a vacuum leak.

 

good luck. If its not a vacuum leek it could be poor fuel or air flow. Black smoke usually indicate that you are burning fuel. Meaning that for some reason or another all of the fuel is not getting burned or ignited in the combustion chamber as it should. For future reference, black smoke is burned fuel and grey smoke is burned oil. One usually hopes for no smoke, but if there is smoke, black smoke is usually better than grey smoke.