2.0 petrol..juddering when i accelerate and engine management light flashes

I agree that it is likely a coil. They are only $23 at Autozone, though I buy OEM parts from autohausaz.com. The light will blink when it is a sever firing error. However, it may not throw a permanent code until the coil is completely dead. If your engine light is on, have Autozone check if it is the coil they can tell you which one. The 03 has no ignition module so that isn't failing (they had them pre-02).

Changing a coil needs no tools... just unplug the wire from the coil, and pull the coil off the spark plug. 1 minute tops. Push the new one back on and plug the wire on. No service bay needed... it's literally a 5 minute job at most. You need a quarter to undo the big plastic screws that cover the engine... there are 3... easy peasy.

Do not drive the car much like this because that one cylinder is not burning gas, so your catalytic converter is. In doing so, it will glow red hot and then fail, and then you get to buy a new cat which is very pricey... like $2500 installed. So a $23 coil is much better.

You can figure out what coil it is by unplugging the wire from each coil while the engine is running. DO NOT UNPLUG COIL FROM SPARK PLUG. You can do more harm that way. When you unplug the coil, either the engine will run worse (good coil unplugged) or not change (bad coil unplugged). If no change, that's the one you change.

If you car is approaching 90K miles, just change all of them. Then you don't have to do this test, and you don't have to go through this problem every 10,000 miles.

It _could_ be a bad plug, but likely not. The chance it's a bad wire is also small.

The only trick in all this is the plug has a little tab on it. If the tab breaks off, don't worry. I have driving 30,000 miles with broken tabs. If you are very worried, use a wire tie to hold it on. But you don't need to.