11:16 10-02-2026

Why diesel engines lose power and how to fix it

Diesel engines were once created by automakers to serve as true workhorses, boasting several advantages: long lifespan, fuel efficiency, simple design, and more. However, it turns out that diesel vehicles gradually lose power and start consuming more fuel over time—and the cause often isn't related to injectors or the turbocharger.

The issue stems from the EGR system: a valve recirculates some exhaust gases back into the intake to reduce emissions, but along with those gases comes a dense layer of soot. This soot-clogged surface inside the intake manifold restricts airflow.

The first sign of trouble is a noticeable drop in performance. The car feels sluggish during acceleration, maintaining highway speeds becomes more difficult, and the engine strains under load. If there are no error codes in the control unit but rough idling appears, it's almost a clear signal that the intake needs cleaning.

The second indicator is increased fuel consumption. A clogged manifold doesn't directly raise fuel usage, but because of the reduced power, drivers tend to press the accelerator more often. For diesels that cover thousands of kilometers on intercity routes, this quickly translates into noticeable extra costs.

Manufacturers don't include manifold cleaning in the maintenance schedule, yet specialists recommend performing it every 50,000–70,000 km. In some cases, replacing the manifold with a new one might be more cost-effective, but often disassembly and mechanical cleaning does the trick. After the procedure, stable idling returns, normal performance is restored, and fuel consumption drops back to expected levels on familiar routes.