Thurston Car Talk: Fuel Injection Cleaning Service


Submitted by Bron at Bron’s Automotive

I am sometimes asked if it really is worth it to perform a fuel injector cleaning service.  The answer is that it depends on the equipment used.  If the only equipment used is a pressurized bottle of product that sprays into the engine’s intake, this helps as far as idle quality goes, and does remove some of the deposits off the back of valves.  This helps the engine to run better, but it doesn’t do a lot to improve fuel mileage.  This procedure is just a small part of the full service performed by Bron’s Automotive.

The bigger and most cost effective part involves a machine with its own small fuel tank.  This machine is a substitute fuel system and runs the vehicle in place of the vehicles own fuel pump and tank, which are disabled for the service procedure. The fuel injection cleaning machine’s tank is filled with a strong mix of fuel and injector cleaning solvent.

First the mixture is run in a circle through the fuel rail, cleaning the inlet screens on the injectors and the pintle on the fuel pressure regulator.  After about twenty minutes, the vehicle is started and the cleaner and fuel mix runs through the inside of the injectors and is then burned in the cylinder.  This cleans the deposits off the inside of the injector which is where the big improvement comes from.

The reason this helps fuel mileage so much is that the injectors plug up at different rates depending on where they sit in the engine.  When the engine is turned off, it “hot soaks” and deposits form on the inside of the injectors at different rates depending on how fast that part of the engine cools down.  When one injector starts plugging up, the oxygen sensor can read the difference, however it can only read the aggregate of the cylinders feeding it.  For example, on a four cylinder motor, if #4 injector begins to plug up, the oxygen sensor will read that and add more fuel.  Since it reads the total of all 4 cylinders, injectors 1,2,and 3 will end up with too much fuel, while injector 4 will still not have enough. (The computer controls the four injectors open time all together)

Having injectors that can’t flow the same amount of fuel is like walking with a limp, (or in this example having a four legged animal walk with a limp).  Performing a full fuel injection system service will make all cylinders produce the same amount of power again.  The result is literally a car that runs like it was new.  This type service will pay for itself at the pump and should be performed every 60,000 miles.

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