I have an interrmittant problem with my 99 Miata (38000miles). It will start and run fine, and depending on it's mood, when I have driven somewhere and killed the engine, it will be very hard to start, and when it does start, it sounds like it is running on only 2 or 3 cyls, strong smell of gas at the exhaust. You can then hit the road, very rough running, and at about 40mph, it is like you flip a switch and every thing is ok for a week or two, then it does it again. Sometimes the check engine light will come on but I do not have a reader yet. I cleared the check engine by disconnecting the battery. Any suggestions??

 

sounds like coil pack. Could be some other stuff, but the coils on these things SUCK. Mine went at about 38k too. Finishlineperformance.com is the place to get the new ones $222. Get NGK blue spark plug wires while your at it (assuming you don't have good wires already)

 

Changed out the coil pak, have not had any more problems yet. Thanks for the help.

 

Hi! New to this forum. I have the same problem (00 Miata LS auto). My mechanic changed the spark plugs, wires AND fuel pump but problem is back in 2 weeks. Im wondering if changing the coil pack solved your car's problem (long term).

 

I'm pretty sure it's the coil pack because that's what governs sparks and paths. The fuel pump probably isn't the problem because your car starts.

 

Remember, also. That when the coil pack goes, it will most likly take the O2 and cats with it. Sorry for the bad news.