i have a 1997 landcruiser4.2gx and am running it on biodiesel i make myself. when the vehicle is started from cold it"hunts" in other words the engine revs from approx 400rpm to 700rpm until it heats up which could take up to 15 miles of driving despite the fact that i may have left the vehicle warming up for 30 minutes before driving. i have used the same biodiesel in a 1997 audi A6 2.5tdi with no problems what so ever. I dont know if it is the biodiesel or the vehicle as i bought it on xmas eve and it was already warmed up and i took it home filled it with biodiesel and it was the next morning when i started it the problem occurred and is still occurring. i live in nothern Ireland so it doesnt get that cold just maybe as low as -5 on a really cold night. any advice would be greatly appreciated. thanks

All I can suggest is stop using the bio-diesel and see what happens

Have you changed the fuel filter.

Can you fit a fuel pre-heater?

hi mate
Have you ever seen the tech characteristic of yr biodiesel?
The problem is that the flash point of either diesel is arround +60-65 C, but biodiesel contains an oil the flash point of which is higher as for normal oil (!) -- so the problem you face is connected with flash point moment especially at cold starting. You' better check with:
- glow plugs performance (they must to be ON forsome time after have started)
- injection quality for all injectors;
- compression rate for all cylinders to evaluate the wearing rate of yr engine.
Cheers/Igor