WASHINGTON — Last April, the head of the Environmental Protection Agency, Andrew Wheeler, proclaimed at an auto show here that he would soon roll back President Barack Obama’s stringent fuel efficiency standards.

That, the administration contends, would unleash the muscle of the American auto industry. It would also virtually wipe away the government’s biggest effort to combat climate change.

Nearly a year later, the rollback is nowhere near complete and may not be ready until this summer — if ever. In January, administration staff members appointed by President Trump sent a draft of the scaled-back fuel economy standards to the White House, but six people familiar with the documents described them as “Swiss cheese,” sprinkled with glaring numerical and spelling errors (such as “Massachusettes”), with 111 sections marked “text forthcoming.”

The cost-benefit analysis showed that consumers would lose more money than they would gain. And, because the new auto pollution rule lacks the detailed technical analyses required by law, the regulations would be unlikely to withstand court challenges.