Romain Grosjean feels something was not right with his Haas car after he struggled in qualifying for the Mexican Grand Prix.
The Frenchman enjoyed a promising start to the weekend on Friday, but from then on he felt the car had changed and has been unable to find an explanation for it.
Grosjean qualified down in 21st position on Saturday and will start only ahead of Jolyon Palmer, who did not take part in qualifying.
The Haas driver is hoping the team can find the root of the problems, insisting the temperature change from Friday to Saturday was not the reason for his struggles.
"We set up everything for the track temperature of qualifying and not for cool weather," said Grosjean. "We knew it was going to be hot in qualy and the race so we didn't look at that.
"We are investigating everything because something is not quite right. Let's see if we find anything, because something happened from FP1 to the rest of the weekend.
"Hopefully we find something because that would mean quite a bit to all of us."
Having been happy with the brakes on Friday, Grosjean continued to have problems with them on Saturday, labeling a "disaster".
The French driver admitted he is keen to test the new ones Haas will try in Brazil.
"Yesterday I was very happy with my brakes and today has been a disaster," he said. "From one day to the next one they don't behave the same way, so I'm looking forward to trying something different."
Grosjean also said that his poor qualifying effort had nothing to do with teammate Esteban Gutierrez spinning in front of him near the end of Q2.
"No, it was on the charge lap," he said.