The Frenchman suspected his problems in Melbourne were due simply to going the wrong way on setup in limited practice running.
But "We're seeing the same phenomenon as in Melbourne and we just don't understand it," Germany's Auto Motor und Sport quoted Grosjean as saying on Friday.
Team technical boss James Allison has one explanation -- 2007 world champion Raikkonen was one step ahead with the E21's development in Melbourne.
And the same is true this weekend.
"He's not had an easy weekend either here or there, because we haven't been able to provide two cars in exactly the same configuration on either occasions," said Allison at Sepang.
In Melbourne, Raikkonen had key aerodynamic upgrades that Grosjean did not enjoy, and the Finn is now enjoying the next wave of development from Lotus' Enstone HQ.
"Here, once again, we only have one set of kit and we've chosen to run that with Kimi and Romain is disadvantaged for that," said Allison.
"We will always try to get two sets available but (it's) not always possible. So he's had a difficult set of circumstances and he's also up against a teammate who is really firing on all cylinders," he added.