The first step in repairing a Bosch fuel injector is to identify the problem. The best case scenario is that the fuel injector just needs to be cleaned.
A fuel injector cleaning kit is available for purchase on many websites, including eBay.com and Amazon.com. These kits include everything required to clean the fuel injector.
Refer to your specific car manual to determine how to use a U-tube to run the gas to the gas tank and how to take off the pressure regulator. Attach the cleaning kit to the car's fuel port, take the fuel tank cap off of the tank and power the fuel pump off. Turn the engine over and let the car run the cleaner through the fuel pump for 5 to 10 minutes. Put the fuel pump back on and restore the fuel cap and pressure regulator. Turn the car back on to determine whether the procedure was successful.
Other issues with the fuel injector include leaks and filter clogs. To fix a leak, the o-ring must be repaired. While the car is cold, remove the fuel cap to remove pressure from the fuel injector. Replace the old o-ring with a new one.
If the fuel injector filter is clogged, first try to use a hammer to unclog it. Gently hit the fuel injector at the site of the clog. If this quick fix doesn't work, a new filter will need to be installed.
If all of these steps fail, a new fuel injector is needed.