I have an Isuzu Wizard (1999, diesel, automatic, fuel injection, 74 000 miles, 3,0 liter, turbo). One morning I started the car and I heard a slow, heavy sound (like an old truck or bus in neutral) about twice per second. The gas pedal was very slow to react. In fact it reacted only after 15-30 seconds.
With the engine still cold and driving on a rugged dirt road, the engine 'breathes' heavily (however, without the car stuttering). Once on the paved road and the engine some warmer, the car runs smoothly. But when stopping (at traffic lights, etc) with the transmission in drive and my foot on the brake, the engine makes the heavy sound again as if it wants to quit, especially when it is still cold. Putting the transmission on 'neutral' or 'park', the sound diminishes. The funny thing is, the gas pedal - once the car is driving - is very 'light', the slightest touch makes the car responds and it runs as hell.
I changed the oil, the oil filter and diesel filter. I had the car scanned (nothing to be found) and I had the fuel lines cleaned. No result.
Who has an idea what might be the problem?