1991 BMW 735i Fuel Injector Replacement Cost

Each time an intake stroke occurs in the engine, the vehicle's computer will send a signal to the fuel injectors, requesting they spray fuel. For heavy acceleration, the duration of the fuel spraying will be longer than if the engine were idling.

When a fuel injector fails or clogs, engine power is reduced and misfires will occur. The check engine light will turn on and, as the issue progresses, the engine may stall immediately after starting, fail to start, hesitate under throttle or vibrate roughly.

It's not smart to drive a vehicle with a fuel injector problem. These issues can cause the car to stall every few moments and accelerate unpredictably, creating a hazard. If the problem is bad enough, the vehicle may not even start, making it impossible to drive.

On average, fuel injectors tend to fail after 80,000 miles, and require little maintenance. To prolong the life of the fuel injectors, follow the scheduled maintenance schedule for cleaning the fuel delivery system and injectors.

If fuel delivery system symptoms are present, the technician will first conduct a visual inspection. If the issue isn't clear after a physical inspection, the technician will connect a computerized scanner to the vehicle to read some of its sensors. If there's a fuel injector problem, the technician would most likely find that misfires are happening frequently on one cylinder. The fuel injector or injectors in question must be tested, and may require removal for bench testing. Any failed components must be replaced, and the vehicle will be checked to ensure the problem is fixed.

Typically, the intake manifold must be removed to access and replace the fuel injectors. This can be a large job that may involve draining the coolant and oil, removing many engine components, and replacing the intake manifold gasket. Some cars, though, are designed with plastic intake manifolds that do not have oil or coolant passages, making this process easier. Once access is available, the fuel injector is disconnected from the fuel rail and electrical connector and removed. The new one is then installed in its place.

When replacing fuel injectors, use high-quality, OEM parts. Keeping the injectors the same will ensure even power across the engine and a proper air-fuel mixture for all cylinders. This should result in smooth running.

When working with fuel, the battery should always be disconnected, and proper precautions taken against fire.

This is not a DIY job. Fuel injector replacement should be left to a professional. The risk of fire is enough by itself, but this repair can also get very complicated. A good amount of knowledge goes into removing the injectors, intake manifold, fuel rail and other components, and if done wrong, it can further damage the vehicle.