Ruf,
It sounds like you are talking about two different things. There's cleaning the injectors and then there's decarboning the combustion chambers.
On a daily driven car that's fed halfway decent fuel, injector cleaning should rarely, if ever, be needed. When a car sits for long periods of time, varnish and gum can build up in the fuel system, including the injectors, and cause problems.
Decarboning the engine is another matter. For this, there are several things you can do.
Integrale4wd's idea will work for the only loosest carbonation in the chamber. Despite the turbulent environment that exists in the chambers at 7000RPM, it's not enough to get the worst of the cabon out. To get it, you'll need to:
- flash it off by water-misting. The sudden cooling presence of the water vapour can cause the carbon to flake off and be ejected out the exhaust.
- chemically attack it. In this scenario, the running engine is fed a solvent slowly enough not to damage it but quickly enough to get it to stall after a minute of feeding, by flooding. Usually, this is done through a large vacuum port near the throttle body. At this point, the chambers are saturated with the solvent, which softens the carbon up. After 15 minutes or so, the engine is re-started and the loosened, softened carbon is much easier to remove using
Integrale4wd technique. If you go this route, I'd recommend an oil change before too much aggressive driving because some of the solvent will have leaked past the rings and into the sump.
Keep in mind that any carbon you loosen and eject will have to pass though the catalytic converter bed. As well, the chemical solution tends to make a hell of a mess with smoke
Maintaining a clean-burning motor is the best idea though. Keeping O2 sensors fresh and air and fuel filters clean is a good start. Highway trips are good. Short trips are bad.
