My car is 2007 Toyota Prado GX manual with the D-4D engine. I was waiting for green light so I put my gear in neutral. After about 1 minute the engine rev dropped below the idle rpm by a lot so it immediately stopped. I had no problem restarting the car. And on my way home the car did the same thing twice. After that when I put the gear into 1 and pushed the accelerator the car received no power and the engine died again. (This problem only happened this once since that day.) The rpm dropping problem occurs basically every 2 minutes while in neutral. Besides problems listed above the car starts and runs fine. I doubt it might be the injectors, so I quoted a mechanic and he said to replace the injectors it will cost me AUD$2k or more. Is it normal? What else could be the possible reasons for that to happen? Thanks a lot. 🙏

1 Answer 1


You may have water in your diesel fuel. Drain some fuel from your water separator and collect it into a clear container. If the fuel separates into two layers, that indicates water.

I don't know your particular engine, but most diesels have their water separator under the fuel filter housing, or integral with the fuel filter.

If you find water, continue draining fuel from the separator until you get only 1 layer in your clear container.

  • Thanks for your reply! I went to a mechanic today and he said the water separator is fine. And he said I need a new solenoid valve, and some pipe is broken under my engine. He said if I got these replaced it might fix the issue.
    – Weeboo
    Dec 23, 2023 at 4:23

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