91 Miata Engine trouble...

[Btothefnrock]

91 Miata 1.6L (Short nose, good keyway)

Will not keep a steady rev under constant load. In the Video, the throttle is being held at around 10%, and you can see the cable is not moving- but the engine dips and revs by itself. Does this cold or hot.

- Idles fine
- Runs to Redline fine
- Not down on power
- No engine codes


What we have done-
-New Coil Pack (tested good)
-New Timing belt +pulleys (double checked)
-New AFM (MAF) (Tried 2 others from running cars as well)
-New Plugs/wires
-Checked for Vacuum leaks (cant find anything)
-New Fuel Pressure Regulator
-New Fuel Filter
-Ran Injector cleaner

What could it be?

Ecu? CAS? Something else?

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[Kaan]

does that car have a TPS?

your video is a sign of a dying TPS on cars what have them.

[NTIman]

does that car have a TPS?

your video is a sign of a dying TPS on cars what have them.

What Kaan said. That sounds pretty right to me, considering the stuff you've replaced already.

[Btothefnrock]

Yup, it was the TPS

Didnt think it would be since it had never been messed with, but sure enough.

Fixed!

[Kaan]

- Idles fine
This tells me the timing is probably ok... not 100% but its probably safe since the issue started randomly.
- Runs to Redline fine
This tells me the coil packs are fine, so are the plugs and wires, and you are getting fuel.
- Not down on power
Same as above.
- No engine codes
This just means in your OBD1 car, that your O2 sensor is good lol

Signs that a TPS is going bad are always at part throttle. They usually are good with no throttle or wide open... they fail at the intermediate areas. At least thats what I have found to be true.