I picked up a non running Miata about a month or so ago, and I am finally getting the time to get it running again. The guy I bought it from did very little to take care of the car. It is an early run 90 base model with A/C.

On a cold start the car will stumble and die. If I wait a few minutes to let the car warm up it will move, but there is still some hesitation. I have done a lot to try and sort it out.

My first issue was was a lack of fuel, I have that run down, good fuel pressure, at the rail now. I have swapped out the following parts with known good functioning parts. The CAS, coil packs, AFM, spark plugs and plug wires, the alternator is putting out 14 volts to the battery as well. I have watched the crank pulley and it does not wobble while the car is running.

About all I have left to change is the throttle position sensor and the idle air control sensor, I have not changed them yet. I have a throttle body that has all of the sensors on it, I will probably just swap out the hole unit.

So, any ideas? Anything I am missing? Google tells me a lot of people have dealt with it, but no one seems to have a solid answer to fix it.

Thanks for your help.

 

Once you get it idling, does it idle smoothly? I could be way off, but have you checked the timing belt? Maybe it is off a tooth or two.

 

Idle is very smooth, and once it gets past the stumble the engine seems to run fine.

 

Double check for crank damage. Aside from that, these cars have a idle control valve that is prone to sticking. It is attached to the side of the intake manifold. You can take it off and try cleaning it out.

 

Any leaks between the AFM and throttle body?

 

There was, but that has been corrected.