Last Friday my 2008 MCS started smelling strongly of engine exhaust. I usually don't smell it if all the windows are closed, but if the windows or sunroof are open I often get a whiff as I'm taking off from a stop, and by the time I get home from work my wife can smell it on my clothes. The odd thing is the smell reminds me of an old car from before cats, or a motorcycle - not a modern car exhaust smell.
I bought the car with 99k miles in March of '19, and it's had a P0420 catalyst efficiency code every time I've run codes and comes back shortly after being reset. I had decided not to mess with it because I've already spent enough doing walnut blast, thermostat housing and crossover pipe, and vacuum pump replacement, and oddly, the code can be present but not illuminate the CEL when there aren't any other codes active. But now, with the smell, I'm wondering if the cat has continued to get worse and finally crossed a threshold.
I reset the codes yesterday morning and have driven about 150 miles in 3 start/stop cycles since then, and the code hasn't returned yet. I also looked at live data and saw that the catalyst temp ran around 712°C while I cruised down the highway at 83mph. Readings from O2 sensor 2 don't look wildly wrong, and the short term and long term fuel trim values all look reasonable, though I don't really know what to watch for.
Please help...with as much as I've had to do with this car in only 4 months of ownership I'm seriously considering selling it and buying something boring for my commute, which is a sad thought given how excited I was about buying it. Losing the ability to drive with the windows down, or possibly spending several hundred more on cats without knowing for sure that's the problem may be the last straw.
I bought the car with 99k miles in March of '19, and it's had a P0420 catalyst efficiency code every time I've run codes and comes back shortly after being reset. I had decided not to mess with it because I've already spent enough doing walnut blast, thermostat housing and crossover pipe, and vacuum pump replacement, and oddly, the code can be present but not illuminate the CEL when there aren't any other codes active. But now, with the smell, I'm wondering if the cat has continued to get worse and finally crossed a threshold.
I reset the codes yesterday morning and have driven about 150 miles in 3 start/stop cycles since then, and the code hasn't returned yet. I also looked at live data and saw that the catalyst temp ran around 712°C while I cruised down the highway at 83mph. Readings from O2 sensor 2 don't look wildly wrong, and the short term and long term fuel trim values all look reasonable, though I don't really know what to watch for.
Please help...with as much as I've had to do with this car in only 4 months of ownership I'm seriously considering selling it and buying something boring for my commute, which is a sad thought given how excited I was about buying it. Losing the ability to drive with the windows down, or possibly spending several hundred more on cats without knowing for sure that's the problem may be the last straw.