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Not sure what the issue is here, NA 1.6litre fairly stock engine, battery is new
Car starts first hit I get about 2 km down the road if I have to slow down or stop the engine will die and not restart, if I leave it 30 mins or so it restarts fine but then dies again after about 2km

Could this be a fuel pump problem, or maybe an O2 sensor ?

It sounds like an electrical component that fails when it gets hot.

Coilpacks do fail when hot but normally only one coil feeding 2 cylinders fails, not both coils, so the car runs really rough on 2 cylinders, rather than stop totally.

Alternatively, is this car still stock? Is there still reasonable heat shielding between the exhaust headers and the AFM? Likewise, are there unshielded aftermarket headers that pass really close to the floor area near the ECU in the passenger footwell?

Is anyone aware of problems with cam angle sensors failing when hot?

Edit: fuel pump/filter failures usually happen sooner than 2 kms down the road and the engines can run fine with a dead O2 sensor.

Possibly the CAS, you can pour cold water on it to cool it when it fails and see if that gets the car to start.

Unlikely to be an o2 sensor.

An MX5 will run without one, and if it's faulty in a way that causes it to foul spark plugs it wont restart until you pull the plugs and wipe them clean.


Fuel pump is a possibility, as they age they can develop an intermitent fault.
An easy (but not perfect) way to test is to see if the symptoms reduce when you have more than about 1/2 a tank of fuel.
The pump is submerged in the fuel when the tank is full, which means the pump doesnt heat up as much during use (since the fuel surrounding it acts as a big heat sink)
With the fuel below half the pump is mostly in air, and can heat up a bit more.

Sometimes this is a sign the pump is a bit dodgy.



As others have said, the CAS (cam angle sensor, big round thing on the back of the rocker cover) is another potential, which can also cause similar symptoms when it starts to get old and fail (again, usually heat related)




So far as actually fixing either of these problems, both are jsut a matter of replacing the part.

The fuel pump is relatively cheap to buy, but many of the non genuine ones come with the incorrect fuel strainer, which can cause issues. so make sure the new one matches the strainer on the old pump, if not re-use the old strainer.
Fuel pump is maybe an hour job if you've not done it before.


The CAS costs more to buy, but is a VERY simple job to replace, being only one bolt.
you will need to have a timing light though, to correctly set the timing once you install the new CAS. (The cas is essentially like a distributor in it's function, but instead of directly passing ignition voltage through it, it sends a pulse to the computer which then sends a pulse to tell the ignition coils when to fire)