Sauber's financial struggles are delaying improvements to the team's 2016 car.
Sauber, along with Renault and Manor, are yet to score a Formula One point this season, with Marcus Ericsson's 12th-place finish in Bahrain their best result so far.
The team has endured a challenging time off the track of late and team principal Monisha Kaltenborn says the issues will have a knock-on effect.
"We have to juggle a few things around [financially] to get things done," Kaltenborn told Autosport.
"There are bits and pieces which, because of our situation, we are just taking time in getting. So when they're all on the car you will see there is going to be a step ahead.
"It's very difficult to speculate what it's going to be like but there will be movement there. We just have to be patient in getting through this phase."