Misfire Cylinder 1: Troubleshooting & Causes

After replacing a broken valve spring, this error now occurs.

The engine runs smoothly at idle. However, as soon as you give it more than 10 seconds of throttle, the first cylinder cuts out. (The fuel line was disconnected for testing).

The ESP settings are almost 95% correct. (For a 1Z engine, the value at number 9 is 100, and at number 2 it is 46).

Then it needs another 2-5 minutes, after which it can be restarted and will run normally at idle.

Here's the translation:

'The following is not:'

1.) Nozzle replaced.
2.) Spark plug replaced.
3.) The hydro has been replaced.
4.) Times checked again.

Hypothesis: Upon the first spring change, the intake and exhaust valve springs were swapped.
Do these have different spring tensions? Or is it impossible to install them incorrectly?

The engine is a 1Z from a Golf manufactured in 1994 or 1996.

Thank you for your help.