Throttle malfunction?

They never heard of it? Haven't they seen the news reports of the runaway Toyotas?

The idiotic engineers have removed the two-ounce common sense throttle cable that rarely caused a problem and replaced it with a sensor on the gas pedal that feeds a signal to a very insane complicated computer which activates a motor to turn the throttle on the engine. This is just screaming for problems and a lawsuit.

Anytime the position sensor on the gas pedal and the position sensor on the throttle assembly do not agree, the computer is supposed to go to a default condition for safety. That's what's happening in your car. The good news is it resets when you turn the ignition switch off and you figured out that works.

One thing to observe is if your foot is on the gas pedal when the problem occurs. That will cause a disagreement between the two position sensors. If that isn't the case, suspect an intermittent gas pedal position sensor.

Caradiodoc

You must have spoken to someone new there or they are just plain being dealers. You want answers you gota pay. You would need to have the vehicle diagnose to see what the problem is. It can be anywhere from a simple software update to a faulty electronic throttle module. Even a poor charging system will cause some major problems. Voltage under 10 volts and the throttle will surely not responde. I strongly recommend you take it in to the dealership and leave it there as long as you possibly can for them to duplicate the problem. Ask for a loaner as well. Here is why you should go to the dealership. Your throttle could still be covered by the 10year/200k mile extended warranty? The 10 year rule starts from the vehicles delivery date so you would need to call Volvo to verify this. If it is still within warranty take it in now! Chances are it is going to be expiring really soon. You will be responsible for the diagnostic regardless of what they find the problem is and whether or not the throttle is faulty or not? But if you take it to another garage you are wasting time and money for something you can probably most likely get for free. Throttle replacement on your vehicle with software reload is around $1000.00 And like I mentioned before, leave it there and do not pick it up until they have duplicated the problem and given you some documented answer and repair so you have a leg to stand on if the throttle happens to fail soon after the warranty repair. If they give you a hard time remind them as caradiodoc mentioned earlier, TOYOTA and call Volvo of North America if you have too as well. Also the Engine Control Module has an extended warranty of 10years/150k miles as well. So if they say it is just a software issue, that is still under warranty. If they say the throttle module software needs updating the ECM software includes that as well so it is still covered. If the throttle does need to be replaced, ask about how the pcv system is. Was that dirty and if it was ok what the readings were. Normal reading min spec is -0.2kpa
If it is at 0 or positive pressure it is dirty. Volvo will pay for the cleaning as well if the throttle needs to be replaced. Good luck to you and keep me posted as to what happens please.