(There’s a slightly updated version of this article available here)
We’ve had many clients who have been sold fuel injection cleaning services by convenience oil change providers, in what seem to us a deceptive way. Fuel injector cleaning is definitely a valid service; clean injectors are critical to proper engine function and efficiency. But knowing why it’s important, how it works, and when it should be done will keep you from paying for this service if it’s not really necessary.
How fuel injectors work
Fuel injectors pressurize fuel and pump it through either a fixed or electronically-controlled aperture, delivering the fuel as a fine, cone-shaped spray to the engine. This mist is easier to ignite than a solid stream, burning more evenly and efficiently. Over time, deposits from the burning fuel build up in the aperture, decreasing the injector’s performance and turning the fine mist into an inconsistent dribble.
Symptoms of clogged injectors
Symptoms of dirty fuel injectors may include:
- hard starting
- rough idle
- throttle “tip-in” hesitation
- pre-ignition (sometimes heard as that ‘pinging sound’)
- poor overall performance
- decreased gas mileage
How to know if your injectors need cleaning
The business end of fuel injectors can’t be seen while the engine is running. Since it can take well over an hour to access and evaluate fuel injectors, injector maintenance is done by time and mileage intervals rather than from direct inspection. We recommend cleaning fuel injectors at least every 36 months or 45,000 miles. Consider it a tune up for your fuel system- it’s really amazing the difference people experience after having a fuel injection and throttle body cleaning on a car that has gone more than 60,000 miles without those services. Many engine parts can be replaced without noticeable improvement in performance, but when dirty injectors are cleaned there can be a distinct before-and-after difference!
How to keep your injectors cleaner longer
2004-and-newer vehicles are less likely to need fuel injectors cleaning as often, because newer designs and today’s better fuel additives reduce fouling. Pre-2004 models benefit from the use of high quality fuel, as this decreases (but doesn’t eliminate) the need for periodic injector cleaning. There are plenty of “cure-in-a-can” fuel system products, but you shouldn’t waste money or risk damage on these potions. The only do-it-yourself fuel system cleaner that works and won’t damage your car is Techron from Chevron. We’re not talking about relying on the low level they put in their fuel at the pumps, we mean dumping a 20oz bottle into the gas tank. For real benefit, Techron must be used at least every 4,000 miles or so. Unfortunately, even when used properly, Techron doesn’t work as well as professional-grade cleaning systems. Your injectors will still need to be properly cleaned eventually.
How to clean your injectors properly
The best commercially available systems for cleaning fuel injectors use a self-contained fuel delivery system with a detergent-enhanced gasoline, pumped directly into the fuel injection system of the engine. MotorVac (the system we use) is just such a machine. This system circulates detergents thru your fuel rail and pressure regulator, using a venture action to remove insoluble material from the injector inlet screens, before cleaning the injector ports, rather than just spraying solvent thru the injector. The complete fuel rail (injectors, screens, hoses, and regulator) is scrubbed clean first, and then the engine is run for about 30 minutes to clean the injector nozzles. These systems hold many advantages over the pressurized-can cleaning setups from years past, (which actually never worked very well at all in our opinion).
Forewarned is forearmed
The best possible reasons to recommend a fuel injection cleaning are appropriate mileage intervals or an attempt to resolve an existing vehicle symptom. If a quick lube tries to sell you a fuel injection cleaning because your air filter is dirty, or because they show you a finger full of dirt scraped from somewhere, don’t be fooled, be angry! Unfortunately most convenience oil change providers try to up-sell services that they can get done in a hurry. (“Up-sell” means bringing in customers with a cheap deal and then selling them more profitable items that may or may not be in their best interest. Unfortunately, this is a very common practice in the automotive convenience market.) Convenience shops are also not equipped to deal with any of the very real problems that may crop up during cleaning. You should avoid buying a fuel injection cleaning service from shops that can’t test your fuel pressure, diagnose or replace a damaged fuel injector, or offer any of the other services you might need as well… or instead.
So, the next time someone tries to sell you a fuel injection cleaning you’ll know how to tell if you actually need the service. If you do need it, make sure that the facility has the best equipment and the expertise and will take the time to do the job right… it’s a waste of your time and money to do it wrong!
