Haas says it has serious work to do before the next race in Baku.
Having earlier looked 'best of the rest' behind the big three teams in 2019, the American team's race pace has collapsed both in Bahrain and now in China.
Team boss Gunther Steiner told Ekstra Bladet newspaper that the problem is tyre temperature.
"When we have heat in the tyres, everything is fine. That's it," he said.
"We understood the problem after Bahrain but could not fix it for here. But we must now find a solution."
Steiner said Haas did not realise it had the problem until Bahrain, due to the nature of the circuits and the weather in Barcelona and Melbourne.
"I do not make excuses, but we just try to get ready for a disappointment if we do not find a solution in Baku," he said.
Haas tried to fix the problem in China with a new rear wing, but Steiner now acknowledges that it will not be that simple.
"It's a combination of things. Otherwise, it would have been easy to fix," he said.
"We have to go back to the wind tunnel and try to find a way to get more energy into the tyres in one way or another. Right now we do not have the solution."
