If there is anything absolutely, positively certain about automotive emissions regulations for Western Europe, it is the utter confusion of it all. In late June environmental ministers of the European Community agreed to introduce lead-free fuel by 1989. But the plan allows members of the European Community to ''jump the gun.'' West Germany, for instance, plans to allow the sale of unleaded fuel in 1986. Switzerland already has an emissions law that calls for the adoption of 1975 United States regulations, including unleaded fuel in new cars, in 1986. Other countries such as the Netherlands and Denmark also may act on the earlier date.
France and Italy have registered strong doubts.
This leaves the European automobile industry up in the air. The Brussels-based Committee of Common Market Automobile Constructors objects to the EC decision, saying unleaded fuel should be introduced in every country at the same time ''to preserve the unity of the Common Market and not to create barriers to trade.''
''Sweden wants to reduce the emissions standards and go one step further,'' says Nils-Gunnar Svensson, assistant manager for emission certification for Saab. It wants to force all manufacturers to use catalytic converters.
Last fall, West Germany made a proposal before the European Community that by model-year 1987 it would adopt current US regulations, which would require catalytic converters on all cars. Because of vigorous objections, the government backed off.
The Association of European Automotive Manufacturers says if a weaker suggestion were adopted, 15 to 20 percent of all German-built cars would require catalytic converters, but no one is sure.
''We can comply with these lower European limits on our compact-model range and medium range without catalysts,'' asserts Dr. Kurt Oblander, head of engine development for Daimler-Benz, ''but maybe on the 8-cylinder models we'll need converters.'' Again, no one is sure.
No matter what happens in Germany, France and Italy oppose the introduction of catalytic converters because of the cost. Also, many of the cars on the roads of France and Italy are small.
''The social impact would be devastating in France and Italy and it's a political issue as well,'' warns Dr. Oblander. To sum up, he asserts: ''We have no idea what will happen.''
If a car has a catalytic converter, it will have to burn unleaded fuel. At present Western Europe has no distribution system for unleaded fuel. Presumably, one would be set up by 1989.
There is another problem as well. The Germans support two grades of unleaded fuel, research octane numbers (RON) 91 and 96. When the proposal was made at Brussels, it looked as though France, Italy, and Britain would agree. Now the French say they want a fuel with RON 94, ''which is just what the Germans do not want,'' reports Dr. Oblander.
''It shows that emissions laws and fuel quality are two subjects that are still controversial and under discussion,'' he says.
All of this is having an impact on car sales in Europe, as motorists wait to see what will happen.
Daimler-Benz reports it will field some models with catalytic converters by 1986, but that poses another problem.
''When we say we will sell some models with catalytic converters, we don't know whether or not our customers will buy them,'' sighs Oblander, even though ''the government says it will give tax benefits to those people who buy them.''
One proposal would exempt owners of cars with catalytic converters from paying a car tax for four years while raising the tax on cars without catalytic converters.
Around and around the emissions talks go. Saab's Svensson asserts: ''There will definitely be stricter air standards in Western Europe, but it will take a long time - perhaps not till 1990 or 1995.
''I don't think there will be standards in the next few years for all of Western Europe.''