Stagnating motot, Reply to white850turbo

[Christophe]

Hi,

Thanks for reply, I'm sorry, my english is'nt very good.
If the engine is on idle, the rmp goes upp and down, from 700 rpm
to 1500 rpm. No Turbo.
No failure codes, no lights on the dash warning. Lights work when starting the car, so there is no bulb failing.
Tomorrow I'm going to the volvo garage again. I let you know...

[UncleBoost]

Does your Temperature Gauge work properly?
Does it resgister at least 1/2 way when the engine is fully warmed up?
Your Temperature sensor can act up and still not give you a code.
Try disconnecting the sensor and see if the problem goes away.
I had the same problem. Changing the sensor corrected it.