2, Fuel injectors:
I started to investigate the fuel injectors.
There are six of them and they are placed at the top of the engine. First you must empty the fuel line system, you can take away the fuse to the fuel pump and then start the engine and let it run until the fuel line is empty, after that there is a valve at the end of the fuel line to let the last pressure goes down. The engine shall be cool when doing this! You see the U-clip on top of the blue fuel injector in the image above.
Beware, there is high pressure fuel inside it, very dangerous, you must empty the fuel line first!
I say, you should not do this if you don't know how to handle this, it could be very dangerous and set your car and house on fire!
It's very limited space here, I had to disconnect the ignition coil cables to get more space.
On the top and bottom of the injector there are O-rings, if they are old they can be cracked and give vacuum leaks. I decided to replace all of them.
Here is how the fuel injector looks. When you take it away, cover the holes on the engine so you don't drop anything inside it! Important is also to test if the fuel injectors close properly, otherwise they leak fuel into the intake and cause problem with the exhaust emission and poor running. I bought a test kit from Hong Kong, 10 Euro.
The old O-rings, you need twelve of them. The type and size are Nitril NBR 70, 7.52 x 3.53 mm.
After one day of work all the injectors were checked and O-rings replaced. There was nothing wrong, but now I don't have to worry about old cracked O-rings, sooner or later they will cause problem.