Renault shares dropped as much as 15 percent Friday (October 18).
That after a warning on profits late the previous day.
The French carmaker says sales are now likely to drop three or four percent this year.
The company picked out Argentina and Turkey as particular problems.
It had previously expected a similar performance to 2018.
Renault said margins would also fall as it struggles to keep a lid on research and development costs.
The news caps a turbulent year.
Former boss Carlos Ghosn is awaiting trial in Japan over allegations of financial misconduct, which he denies.
His replacement - Thierry Bollore - was then dramatically ousted just last week.
Some of Renault's problems afflict the whole sector.
Not least, the cost of developing electric and driverless vehicles.
But it also needs to fix its strained relations with alliance partner Nissan.
Some at the Japanese firm say Renault has too much influence in the relationship.
Then there's the question of how to move on from the era of Ghosn - who dominated the firm for decades.
Right now that falls to new interim chief Clotilde Delbos.
There's no shortage of items on her to-do list.