Mighty Max Fuel Injectors: Are Replacements Common?

The Mitsubishi Mighty Max is a vehicle that has been in production since at least 1984, with models still being driven today. As with any vehicle, the fuel injectors in the Mitsubishi Mighty Max will eventually need to be replaced. The average cost of replacing the fuel injectors in a Mitsubishi Mighty Max is $1178, but this price can vary depending on the specific model and year of the vehicle, as well as the location of the replacement.

There are several signs that may indicate it is time to replace the fuel injectors in a Mitsubishi Mighty Max, including rough idle, loss of power, misfiring, and an odor of raw gas or visible leaks. Additionally, if the check engine light comes on, it could be an indication of a faulty solenoid in the fuel injection system, which would require replacement of the fuel injectors.

Rough idle, loss of power, or misfiring

A rough idle, loss of power, or misfiring in your Mitsubishi Mighty Max could be due to a faulty fuel injector. Fuel injectors are fuel metering devices that spray atomized droplets of fuel into the engine's intake manifold or directly into the combustion chamber. The injector's solenoid and valve are controlled by the powertrain control module (PCM), which optimizes the air-fuel ratio by regulating the solenoid's "on" time.

If your Mighty Max exhibits a rough idle, it could be due to several factors, including issues with the fuel injectors. A rough idle is characterised by an unsteady or erratic engine speed when the vehicle is idling, rather than a smooth and consistent revolution. To diagnose a rough idle, you should first ensure that the base timing is set correctly. You can do this by bringing the engine to operating temperature, shutting it off, and then grounding the 'set timing connector' and pin #10 in the diagnostic connector. After starting the engine, check the idle engine speed, which should be 750 RPM +/- 50 RPM for non-turbo engines and 800 RPM +/- 50 RPM for turbo engines. If the idle speed is outside of this range, you may need to adjust it using the adjustment screw located on the throttle body.

Loss of power in your Mighty Max could be attributed to faulty fuel injectors or other issues within the fuel injection system. The fuel injectors play a crucial role in supplying fuel to the engine, and any malfunction or blockage in the injectors can result in reduced power output.

Misfiring, or uneven firing of the engine's cylinders, can also be caused by faulty fuel injectors. This can lead to an imbalance in the air-fuel mixture, resulting in incomplete or inefficient combustion.

If you suspect that your Mighty Max's issues are due to faulty fuel injectors, it is essential to have them inspected and, if necessary, replaced by a certified mechanic. Fuel injector replacement typically involves relieving the pressure in the fuel rail, removing the upper plenum and any obstructing components, disconnecting the fuel injectors, and installing new injectors with new O-rings.

Odor of raw gas or visible leaks

If you notice an odor of raw gas or visible leaks around your Mitsubishi Mighty Max, it could be due to a leaking fuel injector. Fuel injectors should not leak fuel into the intake manifold when the car is off. If you notice any fuel odor or visible leaks around your car, it is important to address the issue as soon as possible.

The fuel injectors in your Mitsubishi Mighty Max are responsible for spraying atomized droplets of fuel into the engine's intake manifold or directly into the combustion chamber. These injectors are fitted with rubber O-ring seals that can degrade over time due to age and wear, leading to external leaks. An external leak from a fuel injector can pose a fire hazard, so it is important to refrain from starting your car if you suspect a leak.

When dealing with an external leak, a mechanic may need to replace the seals or the entire set of fuel injectors. It is worth noting that the choice to repair or replace will depend on the specific issue with the injector as well as customer preference. Injectors can be serviced off-car or replaced with new ones. If the injectors are serviced, specialized cleaning and test equipment are required.

In addition to external leaks, fuel injectors can also leak internally, adding too much gasoline to the engine. This results in leftover gasoline vapors in the engine after the combustion cycle, which you may smell when idling or at a stoplight. A rich air/fuel mixture can also be caused by a blockage or malfunction in the intake, a faulty oxygen sensor, or issues with other related components.

To summarize, if you notice an odor of raw gas or visible leaks around your Mitsubishi Mighty Max, it is important to address the issue promptly. An external leak from a fuel injector can pose a safety hazard, while an internal leak can lead to excess gasoline vapors in the engine. In both cases, a mechanic may need to replace the seals or the entire fuel injector set, or perform specialized cleaning and testing.

Check engine light

The check engine light coming on can be indicative of a number of issues, and in the case of the Mitsubishi Mighty Max, it could be due to a faulty solenoid in the fuel injection system. This will cause a trouble code to be set in the PCM (powertrain control module), which in turn will cause the check engine light to illuminate.

The PCM controls the solenoid's 'on' time to keep the air-fuel ratio optimised as engine load and operating conditions change. If the solenoid is faulty, it may not be able to maintain the correct air-fuel ratio, leading to a check engine light.

Other potential issues that could cause the check engine light to come on include:

• Rough idle, loss of power, or misfiring
• An odour of raw gas or visible leaks from the fuel injectors
• Major engine repairs, engine replacement, or lengthy storage without use

It is important to note that the check engine light is a general indicator of an issue, and further diagnostics are required to pinpoint the exact problem.

Major engine repairs, engine replacement, or lengthy storage

If you are already planning to disassemble your engine or install a new one, it is a perfect opportunity to service the injectors as a set. All injectors have tiny internal filter baskets that can be cleaned ultrasonically by a professional injector service facility. They will also replace these filters at a relatively low cost.

If you are storing your vehicle for a prolonged period, it is important to consider the impact on your fuel injectors. Gasoline is perishable and will degrade over time, usually within 3 to 6 months, and can damage the fuel system. If your vehicle is going to be stored for an extended period, it is recommended to drain the gas and replace the fuel filter before use.

Additionally, if you are performing major engine repairs or replacing the engine, it is always advisable to install a new fuel filter. This will ensure that any contaminants or deposits built up in the old filter will not affect the performance of your newly serviced injectors.

Fuel contamination

Causes of Fuel Contamination

• Dirty storage tanks: Loose storage tank caps can allow dirt and water to enter, especially during rainfall. Storage tanks may also rust over time, leading to water ingress and the buildup of rusty sediment.
• Stale fuel: Gasoline can go stale in 30 to 60 days, especially when stored in non-airtight containers. Oxidation destabilizes the fuel and leads to the formation of gummy deposits that can clog fuel injectors.
• Particulate contamination: Rust and scale are the primary causes of particulate contamination. Additionally, airborne matter, such as dust and pollen, can enter through tank openings or seals. Damaged filters and hoses can introduce rubber particles and fibres into the fuel.
• Microbiological contamination: Microorganisms, including bacteria, yeasts, and fungi, can enter fuel from the surrounding atmosphere and cause significant damage. Hormonconis resinae (H. res) is a common fungus that can lead to biomass buildup and acidic by-products that corrode metal.
• Water ingress: Water ingress is almost inevitable with stored fuels or fuels used for propulsion. Even small amounts of water can facilitate microbial growth and cause issues.

Common Problems Caused by Fuel Contamination

• Clogged fuel filters: Contaminants quickly clog fuel filters, impacting fuel flow to the engine.
• Damaged fuel pump: Water in the fuel can corrode fuel pump components, leading to pump failure.
• Poor engine performance: Clogged fuel filters and contaminated fuel injectors can result in symptoms such as slow acceleration, rough idle, and decreased fuel efficiency.
• Malfunctioning fuel gauges: In extreme cases, microbial contamination can cause fuel gauges to malfunction and fuel tanks to leak.

Preventing and Detecting Fuel Contamination

To prevent fuel contamination:

• Use reputable service stations with high fuel sales, as they refuel their tanks more frequently, reducing the risk of stale fuel.
• Avoid filling up when the service station's tanks are being refuelled, as sediment may be disturbed and end up in your fuel.
• Regularly change your fuel filter to ensure it effectively captures contaminants.
• Use a fuel stabiliser to maintain fuel freshness during storage.
• Store fuel in dedicated airtight containers to prevent air and moisture ingress.

To detect fuel contamination:

• Use a swab test to check for stale fuel and the presence of water.
• Inspect the fuel filter for sediment buildup.
• Perform fuel tests, such as FUELSTAT®, to detect microbial contamination on-site within 15 minutes.

Frequently asked questions