BAR's Jenson Button boosted his hopes of a strong performance at the San Marino Grand Prix with some quick laps in Friday practice at Imola.
Button has failed to finish a race this season
McLaren test driver Pedro de la Rosa was fastest overall, but Button's time of one minute 21.052 seconds was the best of those who will race on Sunday.
Kimi Raikkonen was third for McLaren and Toyota's Ricardo Zonta fourth.
Fernando Alonso's Renault was fifth ahead of Ferrari pair Michael Schumacher and Rubens Barrichello.
Button, who claimed the first pole position of his career at Imola last year, has failed to finish all three races so far this season.
But BAR completed 6,000km in five days of testing last week and are confident they have resolved their early-season problems.
Ferrari are also trying to iron out reliability issues after Schumacher and Barrichello both failed to finish when the team's new car made its debut in Bahrain.
Schumacher, who has won five times in the past six years at Imola, trails championship leader Alonso by 24 points.
He and Barrichello clocked up more than 40 laps between them in the two sessions.
"We are looking competitive to the others, which is a good sign for the rest of the weekend," said Schumacher.
"The car seems to be very strong in most areas."
Alonso, who leads the standings by 10 points from Toyota's Jarno Trulli, decided not to put too much pressure on his engine. He set his first timed lap of the day with less than 20 minutes remaining.
Britain's David Coulthard finished down in 16th, although he was quicker than his Red Bull team-mates Christian Klien and Vitantonio Liuzzi.
Minardi's first new car for three years failed to make an immediate impression.
Patrick Friesacher was 23rd and last, more than a second slower than Jordan's Robert Doornbos, and team-mate Christijan Albers did not even set a time.
Follow live coverage of the San Marino Grand Prix on the BBC Sport website. First qualifying is at 1200 BST on Saturday, second qualifying at 0900 on Sunday, with the race following at 1300.
San Marino GP first practice times:
1 Pedro de la Rosa* (McLaren) 1min 20.484secs
2 Jenson Button (BAR) 1:21.052
3 Kimi Raikkonen (McLaren) 1:21.704
4 Ricardo Zonta* (Toyota) 1:21.889
5 Fernando Alonso (Renault) 1:21.899
6 Michael Schumacher (Ferrari) 1:22.025
7 Rubens Barrichello (Ferrari 1:22.048
8 Alexander Wurz (McLaren) 1:22.174
9 Giancarlo Fisichella (Renault) 1:22.211
10 Takuma Sato (BAR) 1:22.335
11 Felipe Massa (Sauber) 1:22.791
12 Jacques Villeneuve (Sauber) 1:22.955
13 Jarno Trulli (Toyota) 1:23.343
14 Nick Heidfeld (Williams) 1:23.458
15 Ralf Schumacher (Toyota) 1:26.466
16 David Coulthard (Red Bull) 1:23.815
17 Narain Karthikeyan (Jordan) 1:23.842
18 Mark Webber (Williams) 1:23.964
19 Christian Klien* (Red Bull) 1:24.320
20 Tiago Monteiro (Jordan) 1:24.573
21 Vitantonio Liuzzi (Red Bull) 1:24.626
22 Robert Doornbos* (Jordan) 1:25.172
23 Patrick Friesacher (Minardi) 1:26.620
24 Christijan Albers (Minardi) no time
* = Test driver; not eligible to race.