2003 GT UK Spec, 105k miles. Owned for almost a year and cannot get to the bottom of this weird issue.

So it pops and bangs a lot which I have now deduced to be most likely, unburnt fuel. Its run on 97 or 99, whatever the highest available octane fuel is and it doesn't make a difference.

The coolant temperature sensor died a while ago, I unplugged it and left a spare plugged in externally so I could use it for work, the car read the ambient temperature and worked a treat, both issues went away. I replaced the sensor with a brand new OEM one, problems came right back. Knock Sensor has been replaced but it doesn't throw a CEL.

When driving cold, it feels okay but a bit sluggish, the warmer it gets, the worse it gets. Sparks changed, oil changed, gallery gaskets changed, no issues with burning oil. When hot, if I turn it off and try to restart the car, it splutters and spatters until eventually it lurches into life again.

I'm at a loss and running round in circles and I just want my beast back to normal! Any help you wizards can share would be hugely appreciated 🙏

Pic below is the car in question.

 

Mb install the coolant temp sensor so the ECU has real time data? Just spit-balling...(rolls eyes).

 

I've replaced the old one with a brand new OEM one and it's started to do the same thing again.

 

Hello,
not to split hairs, your earlier post suggested you bought another, plugged it in and left it atop the intake manifold, not actually installed-


The coolant temperature sensor died a while ago, I unplugged it and left a spare plugged in externally so I could use it for work, the car read the ambient temperature and worked a treat, both issues went away. I replaced the sensor with a brand new OEM one, problems came right back. Knock Sensor has been replaced but it doesn't throw a CEL.