I have a standard transmission '90 Miata (recently purchased for low $) and when driving along, if I slowly lift my foot on the accelerator pedal, it doesn’t respond until suddenly the engine speed drops and there is a little jolt. The same thing happens when I slowly increase pressure on the pedal, except then the engine speed suddenly increases (with a little jolt). I tried adjusting the tension on the accelerator cable with no effect. Any ideas what’s the problem?

Throttle position sensor?

Thanks. I had hoped there was something like that. I’ll try to find out where is is and how to adjust/replace it and report back in a few days.