The vehicle had an intermittent flat spot between 2,000 and 2,500 rpm under light throttle, particularly noticeable when going up hills. The symptom tended to disappear after approximately 40 minutes of driving.

The vehicle had been modified with a high flow turbo, a 3 inch exhaust system and an ECU remap, with injectors replaced approximately three years earlier. The customer reported purchasing a bad batch of fuel during an outback trip, with a water separator warning light appearing around 50 km after the fill. The flat spot symptom began soon afterwards. Fuel filters had already been replaced by a previous workshop.