Faulty Fuel Injector Symptoms

Faulty fuel injectors can cause a range of engine issues - and unfortunately, they’re not always obvious right away. 

The initial signs that there is something wrong with the fuel injector could be something innocuous, like the car running slightly rougher than usual. Or perhaps - it’s taking longer to start, even on warmer days. 

Black smoke from the exhaust is another red flag, as is the smell of unburnt fuel. If left unresolved, these symptoms tend to get worse over time, not better.

What Is A Fuel Injector?

A fuel injector is an important part of your car’s engine. 

Its works to deliver an optimal amount of fuel into the vehicle’s combustion chamber – at the right time, in the form of a fine mist. 

That mist allows for efficient combustion, which is what powers your engine.

Modern fuel injectors operate electronically and are controlled by the engine’s computer. 

Faulty Fuel Injector Causes

Fuel injectors can go bad for several reasons. 
The most common is clogging. This is usually caused by dirt or deposits of carbon that build up inside the nozzle. 

Over time, this restricts the flow of fuel and so disrupts the spray pattern.

Other causes include:

• Electrical failure, such as issues with the injector’s internal coil or wiring.
• Seal degradation, which can lead to fuel leaks.
• Contaminated fuel, introducing water or debris into the system.

Sometimes it’s not the injector itself but a problem upstream. Like a failing fuel pump or a blocked filter. This makes diagnosis a bit tricky unless you’re using specialist tools.

Signs Of Fuel Injectors Going Bad

Aside from engine misfires and hard starts, here are some additional signs to watch for:

• Uneven idle: The engine might feel rough or inconsistent when idling.
• Poor acceleration: The throttle response becomes less predictable.
• Increased fuel consumption: If your car suddenly feels “thirsty,” a bad injector could be the reason.
• Check engine light: Fault codes related to fuel mixture or cylinder misfire can indicate injector issues.

In some cases, you might even smell petrol, especially near the bonnet, if a leaking injector is allowing raw fuel to escape.

Will A Faulty Fuel Injector Fail MOT?

It can, indirectly, yes.

A failing injector may not set off alarms during a basic MOT inspection, especially if it’s a minor issue.

However, if the problem affects emissions, which it often does, then it could easily lead to a failed MOT. 

Inconsistent combustion can result in higher CO or hydrocarbon levels - which the emissions test is specifically designed to catch.

If your vehicle has visible smoke, rough idle, or the engine warning light is on, the odds of passing are significantly lower.

Importance of Car Servicing

Regular car servicing is the best way to catch fuel injector problems early. 

During a service, technicians will often run diagnostics, check the fuel system, and listen for telltale engine irregularities.

Servicing also helps prevent injector issues in the first place. Replacing fuel filters on time, using high-quality fuel, and even occasional fuel system cleaner treatments can help extend injector lifespan.

While it’s tempting to delay servicing - especially if the car seems fine - fuel injector issues are exactly the sort of thing that can stay hidden until they become expensive. Routine checks are a small price to pay for peace of mind and reliable performance.