A House Commerce subcommittee agreed yesterday to delay for two years a scheduled tightening of emission standards for autos.

The Senate Enviroment and Public Works Committee had agreed on Monday to a one-year delay.

The existing Clean Air Act requires tighter tailpipe emission standards to take effect on 1978 model cars, which will go into production this summer. The auto industry says it cannot meet those standards. It has been virtually assured of a one-year delay by Congress and the Carter administration. Without the delay, the industry would face a $10,000-a-car fine for producing cars that do not meet federal standards.

But what timetable will be required for 1979 model cars is the subject of intense controversy as House and Senate units mark up Clean Air Act amendments.

The Senate committee, led by Gary Hart (D-Colo.) and Edmund Muskie (D-Maine), would grant no more than a year, arguing that the auto companies have already had several extenstions since the orginal emission cleanup schedule was enacted in 1970.

The House subcommittee, headed by Rep. Paul Rogers (D-Fla.), would give the industry two years to meet the existing standards for emission of hydrocarbons and carbon monoxide and three years to meet nitrogen oxide standards.

The industry wants at least a two-year delay, and it also seeks milder standards on carbon monoxide than those scheduled to go into effect.

The Carter administration has agreed so far only to the one year delay, and has not made a decision on what it will propose after that.

The industry, backed by the United Auto Workers and most of the Michigan delegation, will fight for their version when the House bill reaches the full committee and the Senate bill reaches the floor.

Under existing law, 1977 model cars can't emit more than 1.5 grams per mile of hydrocrabons, 15 grams per mile of carbon monoxide and 2 grams per mile of nitrogen oxides.

If no change in the law is granted, '78 model cars would have to meet standards of 0.41 grams of hydrocarbons, 3.4 grams on carbon monoxide and 0.4 on nitrogen oxides.

The Senate committee gives Detroit until model year 1979 to meet those standards, though it eases the nitrogen oxide standards to 1 gram per mile. The House subcommittee gives Detroit until model year 1980 on carbon monoxide and hydrocarbons, and model year 1981 for 0.4 grams of nitrogen oxide. For model year 1980, the industry is seeking standards of 0.41 on hydrocarbons and 9 grams on carbon monoxide, with the present standard of 2 grams on nitrogen oxide continuing at least until 1982.

Meanwhile the Senate committee faces one remaining controversy - over locating new industries in already heavily polluted areas - before it finishes its bill.

The law now prohibits new industrial pollution in a region that does not meet clean-air health standards, unless a "trade-off" can be arranged to eliminate enough existing pollution to prevent the dirty air from getting even dirtier.

Sen. Lloyd Bentsen (D-Tex.) said that's impossible to do in Houston. "If we closed down every industry in Houston, we'll still be twice the standards," he said. About the only way a new industry could come in, he said, is to purchase an existing factory to put it out of business.

Bentsen said his alternative would permit the Environmental Protection Agency to waive the tradeoff requirement and permit new industry if the state came up with a plan requiring steady annual reduction in the overall level of industrial emissions.

Bentsen called for a committee vote on this "concept," but other senators stalled it off until the staff shapes it into a specific amendment.

Hart said later he believed the Bentsen plan could result in an overall relaxing of existing standards and deadlines. "What we've found in this field is that the only way to get results is to force those results," he said. A vote on the plan is expected today.