Possible Cause

Restricted air intake.

Plugged fuel filter.

Faulty PCM operation.

Improper fuel return system.

Restricted tank-to-pump fuel supply.

Incorrect or contaminated fuel.

Faulty EGR operation.

Worn camshaft or valves.

Nozzle or glow plug compression leaks.

Plugged nozzle.

Faulty TCC or shift points.