Euro Truck Simulator 2

Euro Truck Simulator 2

RJL Scania G, R, R 4-series & Streamline
My engine stalls at 500 revs and won't move forward with the RJL Series 4
The engine stalls at 500 revs and won't go any further when I start a delivery, so I get stuck at the start of the delivery. Only my reverse gear works, strangely enough...
Do you have a solution please?