M-Sport Ford Fiesta driver Basso, who said he made a few mistakes on the 24.15-kilometre Mercatello 1 stage, was nevertheless three seconds exactly quicker than Andreas Mikkelsen on the stage.
Basso is fourth, six seconds behind reigning IRC champion Mikkelsen.
Umberto Scandola is second after finishing fourth on the stage.
“It was a very difficult road but I two made mistakes,” said Basso. “I’m afraid to push.”
ŠKODA UK man Mikkelsen said: “It was very slippery, I can’t find any confidence with the tyres at all. I’m just sliding everywhere and there’s not much we can do.”
Wiegand reported nudging a small tree during one of three moments on the stage prior to service in San Marino.
“The stage was okay but we had two or three big moments when I was too late on the brakes,” said the ŠKODA Auto Deutschland driver. “One time I touched a little tree on the right side. It was really difficult and really slippery.”
Scandola continues to be hampered by the power issue he experienced on the opening stage.
“We had the same problem with the petrol and we have no power,” he added.
Sepp Wiegand claimed his first stage win in the Intercontinental Rally Challenge by winning the opening stage of Rally San Marino.
The 21-year-old German star was 7.5s faster than IRC champion Andreas Mikkelsen on the 19.33-kilometre Sestino test, which started 13 minutes behind schedule.
“It was really slippery but I’m really happy,” said Wiegand. “It was not too much risk, just normal driving and I think I can go faster next time round.”
Umberto Scandola was second fastest despite reporting a possible fuel contamination problem in his ŠKODA Italia entry. Scandola was 2.5s slower than Wiegand in a similar Fabia Super 2000.
Mikkelsen said he adopted a cautious approach after clocking the third fastest time.
“It was one of the most difficult gravel stages I am doing, so narrow and twisty,” said the Norwegian. “I was afraid of hitting things so I took it steady.”
Giandomenico Basso spun twice in his M-Sport Ford Fiesta RRC and was 8.6s slower than Mikkelsen as a result. “It was very difficult and very slippery,” said the Italian, who was fourth fastest.
Patrik Flodin’s hopes of a podium finish are over after the Swede was forced to retire.
Flodin, in a Petter Solberg Engineering M-Sport Ford Fiesta S2000, stopped on the road section heading to stage two with an overheating engine caused by a water leak.
His team manager Graham Clayton, said: “It’s a problem with the engine and he’s had to stop.
“It’s really disappointing because Hankook and the team had really high hopes for him on a surface that he’s very specialised on.
“He was really looking forward to this event and felt happy with the car, the set-up and the tyres.”