The federal regulatory process has slowed dramatically in the past months, Carter administration officials said yesterday, pointing to a marked decrease in proposals of new regulations and long delays in the promulgation of rules already in the making.

In a background briefing, administration officials said 42 of the 109 pending federal regulations the administration began tracking last February have missed significant deadlines on the road to becoming law.

Peter Petkas, executive director of the Regulatory Council, an administration assembled group of regulators from 35 different agencies, said there were four possible reasons for what he called the "slippage" in the regulatory process.

First, Petkas said, agencies are required to do extensive analysis of all major regulations, including cost-benefit studies, and present all possible choices to the proposed regulation to the Regulatory Council for inclusion in its recently created semiannual regulatory calendar.

Second, agencies frequently set deadlines that are then missed as a matter of course, Petkas said.

Third, many agencies are not equipped to do the sophisticated analysis now called for by the Council, and have held up the process while improving analytical skills or hiring outside consultants.

Finally, Petkas said, there is an antiregulatory political climate. He pointed to several attempts in Congress this year to curb the powers of federal agencies.

Petkas acknowledged that one effect of the new analysis requirements has been an increase in paperwork at the agencies, but added that it leads to "a decrease in the paperwork of those who are being regulated."

"We hope that because we are making agencies evalute their actions better, they won't take actions they can't justify," Petkas said.

Public reaction to the first, seminannual calendar published last February, listing not only pending regulations but the various choices and cost-benefit analyses, was "extremely favorable," Petkas said.

At the Federal Trade Commission, outgoing Deputy Competition Director Dan Schwartz (he is becoming general counsel at National Security Agency) will be replaced by E. Perry Johnson, presently assistant to FTC Chairman Michael Pertschuk.

Johnson has worked earlier in the Bureau of Competition as an assistant to Director Alfred Dougherty Jr.

Replacing Johnson will be James Sneed, another of Dougherty's assistants.

Domestic auto manufacturers are exceeding their ability to meet federal fuel economy standards for 1979 model passenger cars, according to new data from the Transportation Department.

A comparison of two reports for the current model year filed with DOT's National Highway Traffice Safety Administration by the four domestic automakers shows that their pre-model-year estimate for the fuel economy they would achieve in 1979 was .5 miles per gallon below what actually happened.

Instead of selling cars with an average fuel economy rating of 19.1 mpg as they had predicted, the automakers instead sold fleets that averaged 19.6 mpg, NHTSA said.

With estimated sales of some 10 million cars in 1979, the additional .5 mpg amounts to about 1.34 billion gallon of gasoline saved over the the lifetime of the 1979 cars.

The estimates and actual figures appear below: (TABLE) Company(COLUMN)Pre-Model(COLUMN)Mid-Model(COLUMN)1979 Market Year Est.(COLUMN)Year Actual(COLUMN)Share GM(COLUMN)19.0(COLUMN)19.7(COLUMN)60% Ford(COLUMN)18.9(COLUMN)19.1(COLUMN)27 Chrysler(COLUMN)20.2(COLUMN)20.4(COLUMN)11 AMC(COLUMN)20.1(COLUMN)19.9(COLUMN)2(END TABLE)