Kimi Raikkonen will lose 10 places on the grid for Sunday's French GP after he was forced to switch engines. The Finn managed only a few laps in practice before his McLaren stopped in a cloud of black smoke, the team later deciding a new engine was required.
Raikkonen, 22 pts behind championship leader Fernando Alonso, had to watch as team-mates Pedro de la Rosa and Juan Pablo Montoya set the pace on Friday.
Ferrari's Michael Schumacher took third in second practice with Alonso fourth.
"The biggest problem was the wind, " said Alonso.
"It made the handling quite unpredictable in the high-speed chicanes, and the car was not consistent lap to lap because of this. But overall, I think we look quite strong."
Giancarlo Fisichella claimed fifth in the second Renault while Olivier Panis, on his return to the cockpit as guest third driver for Toyota, was sixth ahead of Brazilian Rubens Barrichello in the second Ferrari.
David Coulthard took his Red Bull to 10th.
Raikkonen's engine problem ensured a dramatic start to the session.
Just five minutes in, Raikkonen's car began pluming smoke from its engine.
Ten minutes later Red Bull's Christian Klien also saw his session come to a premature end when he slid into a tyre wall.
The Austrian lost control at the entry to turn seven and slid sideways into the barrier at high speed, knocking off his front wing.
De la Rosa had the best of the day. The Spaniard was fastest in first practice ahead of Alonso with a lap of one minute, 14.778 seconds and followed it up with a one minute, 15.129 second lap, over half a second ahead of Montoya.
Meanwhile, the French Grand Prix is being targeted by a group of donkey-riding protestors.
The anti-consumerism group are mounting their fourth annual attempt to disrupt the race by riding a donkey convey from Lyon to Magny-Cours.
As practice started, reports were already coming in of traffic congestion 12km from Magny-Cours.
The group plan to march on the circuit on race day, raising fears of serious traffic problems.
Second practice for French Grand Prix:
1. Pedro de la Rosa, Spain, McLaren-Mercedes, 1:14.460
2. Juan Pablo Montoya, Colombia, McLaren-Mercedes, 1:15.129
3. Michael Schumacher, Germany, Ferrari, 1:15.204
4. Fernando Alonso, Spain, Renault, 1:15.242
5. Giancarlo Fisichella, Italy, Renault, 1:15.380
6. Olivier Panis, France, Toyota, 1:15.483
7. Rubens Barrichello, Brazil, Ferrari, 1:15.605
8. Jarno Trulli, Italy, Toyota, 1:15.774
9. Ralf Schumacher, Germany, Toyota, 1:15.925
10. David Coulthard, Britain, Red Bull, 1:16.371
11. Jacques Villeneuve, Canada, Sauber-Petronas, 1:16.430
12. Jenson Button, Britain, BAR-Honda, 1:16.597
13. Felipe Massa, Brazil, Sauber-Petronas, 1:16.753
14. Takuma Sato, Japan, BAR-Honda, 1:16.890
15. Vitantonio Liuzzi, Italy, Red Bull, 1:16.987
16. Mark Webber, Australia, Williams-BMW, 1:17.107
17. Nick Heidfeld, Germany, Williams-BMW, 1:17.192
18. Robert Doornbos, Netherlands, Jordan, 1:17.574
19. Narain Karthikeyan, India, Jordan, 1:17.790
20. Christijan Albers, Netherlands, Minardi, 1:18.508
21. Patrick Friesacher, Austria, Minardi, 1:18.814
22. Christian Klien, Austria, Red Bull 1:18.897
23. Tiago Monteiro, Portugal, Jordan, 1:19.186
24. Kimi Raikkonen, Finland, McLaren-Mercedes, no time