Stumble/Hesitating Throttle Response

  1. My model of MX-5 is: 1990 V-Spec Eunos Roadster 1.6
  2. I’m based near: Canterbury
  3. I’m looking for technical help or recommendations on: Stumbling/Hesitating on throttle application

I bought it non running after it had sat for 10 years. The fuel pump had seized, put a new one in and fired up immediately.

Since then I have replaced, Sparks, Coil pack, HT leads, fuel filter, AFM, fuel pump, oil filter.

It starts and idles perfectly however when I apply the throttle it stumbles/hesitates, the rpms visually and audibly reduce before increasing. The issue then got worse to the point it was stalling with full throttle. I must confess this is only when I drained the fuel (had been running it previously with only new fuel on top of old) replaced the fuel filter and bought a new AFM. Since it has improved slightly but is still noticeable. The issue also improves when is warm.

I have checked as best as I can for air leaks. I have also ordered a new ECU temp sensor. I’m also wondering weather this is a clogged injector due to me running it for a bit with the old fuel.

Thank you for reading, any advice would be greatly appreciated!

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