Hey all,

Been awhile since last post. 1995 DeVille 4.9 been running good till late. We have almost 90K with excellent service. Recently, exhaust has really been smelling bad and mileage has dropped considerably. Car (http://www.cadillacforums.com/forums/#) STILL runs like a scalded dog but smells like a scalded dog which has eaten rotten eggs.

Haven't pulled codes yet. Am leaning towards either O2 sens or MAF sens. Any ideas or numbers of things I can check I would really appreciate.

Safety & blue skies,

Jeff

If you get codes, they should point out if it's one of those sensors... If not, might want to check and see if your catalytic converter has been clogged. (backpressure from this could cause an exhaust leak as well.

It is the cat!

Check the FPR first (easiest and cheapest). Rich exhaust will smell like sulfur.

rotten eggs smell is a dead giveaway to a bad cat....

I bet a sensor has gone bad, which has caused the ECM to set the car to run full rich.

When I intentionally disconnected O2 sensors, the computer didn't say anything... I have the same car as you do. I am not sure what it means, but the computer may not be as sensitive as you wish to detect faulty O2 sensor.

Also, I don't think our cars have a MAF, but a MAP. That is located behind the TB.

You can check if they are working fine or not. Get in the diagnostic mode. You can see BARO, MAP, and O2 sensor cross counts to check them. I forgot which data corresponds to what. They are all shown as PDXX (XX being 2 digits number)...

I was having the same problems with my 2000 Deville. The exhaust would smell horrible, my friends in the car would look at me funny as if I was the cause of the foul gas at a stop light or parked. Turns out, it required premium gas. But with the price of gas, I can stand the look I get from my friends. I'm replacing the cat on it reguardless...

2000 does not require premium. Compression was lowered in 2000 to allow for regular.