exhaust smells very rich

When I pull up to a stop, I get a strong smell of very rich exhaust, almost Diesel smelling. The car runs fine otherwise. I assume a sensor is to blame but which one? Could it also be the PCV? I can hear it clicking back and forth but if it fails, do I start re-burning crank case oil vapors or is that it's purpose and now it's not? Need to figure it out cuz this thing is pungent.

Do you have any oil leaking that might be getting on the exhaust system somewhere?

Check for a fuel tank leak getting fuel on the exaust pipe, look carefully, it may only leak when brakeing. These things are famous for crakes in the PLASTIC tank.

Thanks, I'll check it this weekend. The smell seems to come and go. Yesterday my tank was nearly full and I had the smell, today I'm at 3/4 and I didn't notice it. It's a 93 by t he way.