Does Your Diesel Engine Have Power Loss When It’s Under Load?

Diesel engines produce a lot of torque. This is why trucks and other cargo vehicles have them. They can perform well even when under heavy loads, such as when climbing a hill or towing heavy cargo. But over time, there’s a chance that your diesel truck might be losing power while driving. If a diesel engine lacks power, then this can be a sign that something’s wrong.

What causes power loss in diesel engines? There are a lot of problems that can occur that can interfere with your engine’s ability to produce power.

Reasons Why Your Diesel Engine Loses Power

Clogged Catalytic Converter

Proper exhaust flow is important. Any backpressure created along the exhaust system will create resistance during the cylinders’ exhaust stroke.

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Pro Tip: Older diesels didn’t have catalytic converters, newer diesels do.

Malfunctioning Exhaust Backpressure Valve (94-2003 7.3L Power Stroke)

From 1994 to 2003, the Ford 7.3L Power Stroke turbocharger included an exhaust backpressure system to provide more heat to the coolant for better cab heating and to initiate higher defroster temperatures sooner in a drive cycle. The exhaust backpressure system operates during low-load, low-rpm operating conditions.

At high-load, high-rpm conditions, the backpressure system is disabled to allow better exhaust flow from the engine. The backpressure device is a butterfly-type valve located at the turbocharger outlet that is controlled by a solenoid and an oil pressure driven piston. If the EBP butterfly valve is stuck closed, it will have the same effect as a clogged exhaust.

Clogged Diesel Particulate Filter

The diesel particulate filter (DPF) traps harmful particulates and soot before it’s released into the atmosphere. This part can sometimes get clogged, which will increase exhaust system backpressure and require the engine to waste energy expelling exhaust gases, causing a reduction in power.

Clogged Fuel Filter

Dirty fuel can have debris that can get stuck on the fuel filter, which will decrease fuel flow and pressure. When the diesel fuel filter gets clogged, it’ll start depriving the engine of fuel, especially when the engine is under load. This can be a reason why a diesel engine loses power when going uphill.

Insufficient Fuel Pressure

A malfunctioning fuel pump or diesel injection pump is another reason why your engine could be losing power. The fuel pump sends fuel from the fuel tank to the engine. Meanwhile, the diesel injection pump receives fuel from the fuel lines and pushes diesel into each cylinder.

If these pumps are producing insufficient pressure, your engine will be deprived of fuel, resulting in reduced power.

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Dirty Air Filter

The air filter prevents contaminants like dust and bugs from entering the engine’s intake, which can damage the engine. If the air filter hasn’t been cleaned or replaced in a while, the contaminants can restrict airflow and prevent the engine from generating enough power.

Leaking Intake System

Just like a dirty air filter, a leak somewhere in the vehicle’s intake system, such as on the intake manifold, turbocharger, or charge air cooler is going to reduce the amount of air entering your engine. A leak in the intake system, particularly after the turbocharger, is going to reduce your engine’s power output since air is necessary for combustion.

Faulty Sensors

Sensors such as the mass air flow (MAF) sensor and oxygen sensor are important since they send information to the engine, which helps it optimize engine functions. When these sensors malfunction, the powertrain control module (PCM) can mismanage ignition timing, causing issues such as insufficient power under load.

Faulty EGR Valve

The EGR valve recirculates exhaust gas back to the engine to lower engine temperature and reduce emissions. If an EGR valve malfunctions, it can allow exhaust gases to circulate back into the engine during inappropriate times. This can cause the engine to perform poorly.

There are a lot of issues that can cause an engine to have reduced power. Your vehicle’s PCM can detect some of these issues and can illuminate the check engine light on your gauge cluster. If your check engine light is illuminated, then there’s a good chance your vehicle has one of these previously mentioned issues. Your best course of action is to go to a reputable auto shop to have the problem diagnosed and fixed.