I have a total of 4 fuel injectors in my hand, and was wondering how I'd go about cleaning them, and how to tell if they're any good. I do get a loss of mileage, and my engine hesitates a lot. And i did receive a p0171 code. So i thought i'd check the injectors first.

But do you guys know any good ways to clean this? It's ridiculous to go in to a professional and pay all that money when i have them in my hands.

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these are all four, but the very top one has a crack around the ring, would that classify as a bad injector that needs replacing?

all of my O-rings look perfect, so I don't think that's an issue.

  • Is the cracked part rubber or hard plastic or what? Aug 5 '14 at 21:01
  • @Paulster2 it's like a plastic type deal. Aug 5 '14 at 21:33
  • A crack/break in that plastic part isn't a big deal, as long as the rubber o-ring is in good shape it's fine.
    – Ben
    Jan 23 '16 at 14:57
  • I have 1AZ engine and have replaced it with anothor one nd it doesn't rev what it be
    – kmox
    Feb 12 '17 at 19:25

The injectors you have shown in your pictures are not servicable items. They can be tested using the appropriate service machinery. You should be able to get a new set of external seals though. When tested professionally they are tested for their electrical performance, delivery performance, and spray pattern over varying fuel pressures and voltages. Anything other than a professional test is a waste of time and inconclusive. There is also a safety concern when they are interfered with in an amateur way. Modern vehicles are a lot more complex than ever before, especially because of the all-embracing electronics used today. Service centres and garages have to make a large investment in their equipment and this has to be charged back out. If the cost of testing is too great for you to afford then you are left with the only option of buying new replacement injectors. In the tank fuel additives never live up to the blurb on the can, and can even make matters worse by releasing contaminates to go around the fuel system.


You have a couple of choices here, neither of which includes you cleaning these yourself. You do not have the equipment or chemicals to correctly or efficiently clean and flow test these injectors. It is important to ensure each of the injectors flows the same amount of fuel in a given time at a specified fuel pressure. Only a professional service can provide this for you. You cannot just spray your injectors with carb cleaner and expect them to be clean and work correctly.

This leaves you one of two options:

First, you can replace your injectors with new ones, or for a better price (approximately half), you can purchase rebuilt ones.

Secondly, you can have yours sent out for rebuild. In doing so, the rebuilders will clean yours (probably with an ultrasonic cleaning machine, something like what is used to clean jewelry, but with chemicals to clean the injectors correctly and safely), replace any worn parts, check the electrics (solenoids, connections), and flow test them to ensure each is flowing the correct amount and the spray patterns look good. This process is a little cheaper than buying rebuilt ones, but you have the time factor involved in shipping and down time of your vehicle.

You made mention of your o-rings looking good. If these are the original o-rings, I can almost guarantee you they need to be replaced. While there might not be any visual damage to the o-rings, they do harden over time and conform to the hole which they have been stuck in for all those many miles. If they are left alone, they will provide many, many miles of worthy service. Once they are dislodged from their holes, trying to put them back is not only difficult, it will almost assuredly allow for leakage of air past them, exacerbating your lean condition. New o-rings are cheap. If the o-rings are original, they need replaced. Ensure you put fresh oil opinion them to help in insertion and to help guard against damage during installation.

Equal flow is important to the injectors. If they do not flow equally, you might have lean conditions in one cylinder while having a rich condition in another. This will create a power imbalance in your engine which creates more wear and tear. Your engine will last much longer if it is functioning correctly, as well as it will run much smoother all the while.


Put the injectors back into the car. Add Marvel Mystery Oil (or automatic transmission fluid) to your gas tank at fill-up at a treat rate of 1 oz. per gallon. Drive the car immediately in stop-and-go traffic for 10 minutes, shut off engine for 10 minutes, then drive on the highway at 70 MPH for 10 minutes. Repeat this cycle multiple times, for at least an hour, and allow the mixture to penetrate at least two days.

When your tank drops to 10 gallons of gas, add one can (15 oz.) of Berryman B12 Chemtool and one can catalytic converter cleaner (or simply 2 ounces of Berryman's for every gallon of gas). Immediately drive the car on the highway for 30-60 minutes, then "floor" the car at wide-open-throttle (WOT) from 50-80 MPH. Repeat the full throttle blasts at least six times, but up to 30 times if the cat. & sensors are very dirty. Be sure the cooling system and transmission are flushed and working properly beforehand. Turn the heater and fan on maximum, with windows open, when performing the WOT blasts.

The Berryman's and cat. cleaner evaporate out of the gas tank after about 24 hours, so be sure to run the car hard right away. The Marvel Mystery Oil never fully evaporates. The two products – Marvel Mystery Oil & Berryman”s B12 Chemtool -- work together and will never damage any components of the car.

The combination of heavy & light naphtha, volatile solvent, heat & pressure is very effective. I have resolved many injector issues in this manner. At every fill-up, continue adding Marvel Mystery Oil at a treat rate of 4 oz. for every 10 gallons of gas. It will continue to clean deposits. Every fourth fill-up, add one can of Berryman's and drive at highway speeds.

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