For this check, you do not need the vehicle running or the ignition to be on. You will be checking Ohms.

First, remove the corresponding electrical connector from the injector you wish to test.

Now you should see two metal prongs (contacts) inside where the connector was. Set your meter to the Ohms (Ω) setting.

Next touch your red meter lead to one injector contact, and the black meter lead to the other contact. Since you are in the Ohms setting, it does not matter which lead goes on either contact.

With the meter in the lower Ohms setting, you should get around the same resistance on all your injectors. If one injector is reading much higher or lower than the rest, it is most likely bad. If you get an open (O.L.) or zero Ohms (shorted), then your injector should be replaced.  

Be very careful while near a running engine, make sure you do not have on loose clothing or jewelry that can be tangled into the motor belts and pulleys. Always think safety first!

You could also check a fuel injector by carefully putting a long screwdriver directly on the injector while the engine is running.

Using a long shank screwdriver, hold the screwdriver handle up to your ear, the shank on the sensor itself, and you should be able to hear a clicking noise. If not, then it is probably either clogged or the circuit inside is open.

If in doubt whether the injector is bad or not, try switching the suspected bad injector with a known working one and listen again, sometimes it's just the area you are trying to listen at.

If all goes well and you do not find any bad meter readings, and you still have a misfire problem, then you might have a clogged injector. In this case you will need to clean the fuel injector.

There is on-car cleaning, and off-car cleaning.

On-car cleaning is cheaper to the consumer and can be done by the average garage mechanic, but does pose some risk because you will be injecting pressurized detergent through the fuel system.

You will need to stop the fuel flow to the engine by removing the fuel pump, and plugging the fuel lines. Then connect pressurized cleaning detergent into the fuel injector system and on into the engine. After cleaning, re-connect the fuel lines and install the fuel pump. Finally start the vehicle as normal, you should now notice increased performance and improved fuel economy.

Off-car cleaning at a auto repair shop costs a little more (usually 35-50 dollars an injector), but will offer a lot deeper cleaning than on-car. This is probably the better option and it is much safer too.

A quick search of the internet will give you specific instructions on how to clean fuel injectors yourself if that is the route you choose. We will not go into detailed cleaning instructions of the injectors here at this time. 

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