I have a 1993 Miata with 230K miles - original owner. My problem ( one of many) was a severe flat spot when starting out that goes away after driving ten minutes or so. When I say severe I men the engine went totally flat when the accelerator was pushed down causing me to propel forward. At first I thought it happened more when cold and the weather was damp so I replace the plug wires which did not help. Later it started doing it when cold or slightly warm after sitting for 15 minutes or so and the weather did not make a difference. I have been living with this problem for over a year. Finally, I took it in and was told that a code for the camshaft angle sensor came up. After replacing the sensor it is 80% better but it still does hesitate occasionally and there is an intermittent lope in the engine at idle. The shop I took it to did some other adjustments and cleaned the throttle body ( I think) but no codes come up and they don’t know what’s wrong. Just passed smog - Suggestions?
Problems like this that occur during the first 10 minutes after a cold start usually point to a failing ECT (engine coolant temperature) sensor.
At that mileage your camshaft may be wearing out.