faithful_lothario

The CEL just came on in my car. It's a 1995 C280 with 112500 miles. The car isn't having any problems running. I have been getting really bad gas mileage close to 20MPG on the highway, so I think my O2 sensor might have gone bad.

I'm going to Auto Zone to get it checked tomorrow, but I wanted to know if I had to change the O2 sensor immedietly or if I could wait a while before replacing it?

AK

ohlord

you don't have obd2 do you?with the port under the dash?Don't know if autozone reads obd1 anymore with the underhood socket.If you can't get the codes read because it is the earlier system,try cleaning the maf first, a failing one can cause mpg problems.Then see if the code clears.If not before you spend the money to install new O2 sensors,get it on a scope and have the O2 values checked to see if you really need them.If a pre cat sensor failed you would not want to drive it that way for to long a time,fuel demand gets way out of whack and can fry the cat converter.
ohlord
look under the drivers dash and hope the diagnostic port is there for you to get the codes.
CRC brand maf cleaner at autozone,cleaning procedure on benzworld.org w210 diy section.keep us posted.

MTI

There's more than one O2 sensor in the system, with different prices, so check the error code before buying anything.

faithful_lothario

so it turns out that my upshift vacuum line had to be replaced. Cost me about $600 at the dealer

guanabara

wow that sounds quite high price.