Car is running rich

[MrAbbs325is]

So My car is running really rich which I believe ruined my cats. You think it has anything to do with a thermostat? or something else

[David Mc]

The safest bet is to do the stomp test and see if there are any fault codes stored. This link will explain how to do the test and what the codes mean http://www.pelicanparts.com/BMW/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm . If the thermostat is stuck open or the temperature sender switch on your car is cactus it may also be constantly indicating to the DME that the engine is cold, resulting in a rich mixture.

[Andycapps]

+1

On your car, there are many sensors that work together to feed information to the DME. Based upon the sensors inputs the DME adjusts the fuel mixture accordingly. Check to see if you've got any fault codes stored even if the check engine light isnt on right now, you might still have one stored.

[Franky goes]

Likely a bad oxygen sensor. Check the codes as mentionned.