FAQ-24

When Do I Flush My Fuel Injectors?

I do not believe in flushing your injectors as part of your routine maintenance. There will come a time where the cost of the yearly flushes will exceed the cost of new injectors installed. At customers requests, we have flushed many, many injectors both port fuel (where each cylinder has it's own nozzle) and TBI (throttle body injection, where there is one or two injectors providing fuel to all of the cylinders) with all kinds of chemicals, and we have never had a customer say it made a nickels worth of difference.

There are late model Ford and General Motors cars that have injectors they don't want to be flushed and if you do, you run the risk of ruining them.

Often times when someone tells me an injector flush fixed a problem, after further questioning, I determine lots of other work was done at the same time.

My advice is to wait until you have a problem related to the injectors, then either have them pulled and professionally cleaned and adjusted or replace them all. If this happens it may cost you $500 to $800 for a port fuel injected car or much less if your car has only 1 or 2 injectors in a throttle body. If the replacement is necessary in year seven of your cars life, you'll have $450+/-  in your pocket that you didn't spend on flushing over the last 7 years.

Now there are reasons to flush your fuel injectors. Often times we will flush injectors in an effort to determine if the injectors are part of a problem. Otherwise, if we flush the injectors and the problem changes, either for the better or the worse, we know the problem is injector related. We use on the car injector flushing for diagnostic purposes only. However, there are times we will flush the injectors on the customers car in an effort to clean or repair them. This typically happens when a new injector is very expensive ($175-450) and the customer doesn’t want to spend the money to replace the injector or pull it to be tested and ultrasonically cleaned. Then a $75-175 injector flush is a good gamble.

We are just now seeing a lot of fuel injector problems in 80's and 90's port fuel injected cars. An easy conclusion that could be drawn would be that, unserviced port fuel injectors, will last 5-7 years. With the fuel improvements over the last 4-5 years, we should see injectors live even longer.

If you insist that your injectors are cleaned, by far the best way is to have them removed and cleaned and balanced by a professional shop that specializes in that type of work. That way they can measure their success. For instance, they will first test the flow of each of your injectors and note that number. Then they will ultrasonically clean them, just like they clean fine jewelry.

Then they will retest the flow and see some improvement. The trick is to keep cleaning until all the injectors flow the same. So you may start with all the injectors flowing at 15cc with a lousy spray pattern, then after numerous cleanings, you can bring them all up to 25cc with a fine mist spray pattern. If you originally had one injector electronically shorted and you had to replace it with a new one, which happens all the time, you can keep cleaning and testing until all of the older injectors flow like the new one. Doesn’t that way of injector flushing just sound a lot better than a $49 a can of cleaner squirted through the fuel system and hope like heck something ends up better?

What happens to the fuel injectors
when they go bad?

Two things make injectors bad, they get plugged up which can be fixed or they go bad internally or electronically and this cannot be fixed. Injectors that are shorted or bad electronically must be thrown away.

The real problem is when injectors are subjected to "hot soak". This occurs after you have driven your car and the motor is fully warmed up, then you shut the motor off and let it cool down. During this cool down time, any gasoline residue remaining is being baked on the injector tip. The miles driven between "hot soaks" is the difference between having to address an injector problem at 50,000 miles or so and being able to double that mileage. Consequently, someone who drives 100 miles then shuts the car off (which equals one "hot soak") is much less likely to have injector problems than someone who stops and turns off their engine 10 times in the same 100 miles.

If you insist that your injectors are cleaned, by far the best way is to have them removed and cleaned and balanced by a professional shop that specializes in that type of work. That way they can measure their success. For instance, they will first test the flow of each of your injectors and note that number. Then they will ultrasonically clean them, just like they clean fine jewelry. Then they will retest the flow and see some improvement. The trick is to keep cleaning until all the injectors flow the same. So you may start with all the injectors flowing at 15cc with a lousy spray pattern, then after numerous cleanings, you can bring them all up to 25cc with a fine mist spray pattern. If you originally had one injector electronically shorted and you had to replace it with a new one, which happens all the time, you can keep cleaning and testing until all of the older injectors flow like the new one. Doesn’t that way of injector flushing just sound a lot better than squirting a $49 can of cleaner through the fuel system, then hoping something is made better? Of course that way, there was no measurement made to compare the end results with, so no one can say the flush did or didn’t do anything.

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