Fuel Injector Cleaning More Than Meets the Eye
Even skeptics, who view most chemicals as snake oil, can see the difference this service makes

IT'S ALMOST ROUTINE. A customer complains of poor performance, rough idle, hesitation, and so on. There was a time, not so long ago, when you would suggest a tune-up. It was almost a knee-jerk reaction. But, since this car is fuel-injected, you confidently tell Mr. Customer that his problem is dirty fuel injectors. It's the modern knee-jerk reaction.


Is fuel-injector cleaning the magic cure-all for all performance problems? Hardly. It's no more a panacea than an ignition tune-up used to be. But understanding this service makes it something you can offer to maintain good drivability, perhaps preventing problems instead of correcting them. Remember, that was the whole idea behind the periodic tune-up.

Tips About tips - The initial reason port injectors got a lot of attention was because deposits formed at the injector tips. During a hot soak, the lighter molecules of fuel evaporate and the heavier aromatics and olefins oxidize to form gums and resins. Once the process is started, it continues and gets progressively worse. Note that deposits form only when the engine is off during hot soaks. Deposits do not form when there is fuel flow, as when the engine is running.

Carbon Caution - It may not be news to you, but some technicians are still unaware of the drivability problems caused by carbon buildup on intake valves. This problem starts long before the driver notices any difference in drivability and gets progressively worse. This carbon buildup not only reduces the effective amount of intake valve opening, but also steals some of the fuel discharged by the injector. These carbon deposits tend to be somewhat porous and act as sponges trapping some of the fuel.

This usually causes cold drive away problems before the fuel injection system goes into closed loop. As the engine warms up, some of the fuel stored by the carbon sponge vaporizes and is carried into the cylinder when the valve opens. The remaining fuel absorbed by the carbon contributes further to carbon buildup, baked on by the heat present during hot soak.

Deposit Defense - The automobile manufacturers pleaded with the oil companies for gasoline detergent additives to help curb deposit formations. Since then, additives have been introduced that have proved effective, with some trade-offs. Research shows that some detergents used to reduce injector plugging actually contribute to intake valve carbon buildup, or coking as it is commonly called.

Meanwhile, injector design changes have taken place. Many new injectors no longer use the pintle design and are less prone to tip deposits. The two most common new injectors are the ball and seat design and the disc design. Both are more resistant to the effects of deposit buildup than their pintle counterparts, but they're not totally exempt from the deposit problem.

Service Strategy - The various chemicals and systems currently available all claim to clean dirty port injectors and, in some cases, TBI injectors. The missing element for this service, however, is a recommended interval for when fuel injectors actually should be cleaned. Service frequency seems to be a matter of opinion. Some shops elect to clean injectors only when a customer has a drivability complaint.

Others take a more assertive approach. They routinely perform the service at mileage intervals, or as part of a scheduled tune-up. This is a good plan when you consider that some of the services that you used to perform during a tune-up aren't necessary any longer. Who's right? Let's discuss a few more points and you decide.

Some manufacturers of injector cleaners claim that their systems do more than just clean injectors. They claim their products remove intake valve deposits and combustion chamber deposits. It becomes apparent that drivability problems with fuel-injected engines may be the combination of several problems and when you "clean injectors", you really may be cleaning the intake valves and combustion chambers as well. Of course, analyzing what you really did is not important because, to your customer, all that matters is that the car runs better.

Fuel injector cleaning is a service that you should have in your bag of tricks for today's cars, especially when you consider the added benefits of intake valve and combustion chamber cleaning. The service doesn't take much time. It can be extremely profitable. And the customer usually feels an immediate drivability difference. The feeling of renewed pep and performance is akin to the results of new plugs, points and a condenser.

Routine injector cleaning is like a tune-up for the fuel system.