failed car emissions test

We need the make, model, engine, year, mileage and where the test was performed.

89 cadillac sedan deville, 4.5L v8, 85k miles, and the test was performed in DC

That is a tough question. That engine has been historically a dirty burning engine under modern standards. When it was built it satisified all the requirements. Because of the aluminum engine it has had some problems with oil consumption and over heating. If you engine has over heated one time it probably won't pass.

I would start with all vacuum hoses and the air cleaner. It could use a set of plugs, new wires, distributer cap and rotor. Look for obvious oil leaks. If the engine is using oil by leak or burning it probably won't pass the DC requirements.

It's difficult answering your questions because I am not standing threre looking at the engine.

Good luck