"Vibrating Engine Problems on 2003 Cadillac CTS"

Black 2003 Cadillac CTS

I have a problem with the engine on my 2003 Cadillac CTS. When I start the car, it start’s to vibrate but like in slow motion. I’m thinking that the problem can be the spark plugs. But I don’t know that much of cars. It also have a terrible gas mileage. What can be the problem?

Answer: It sound like your oxygen sensors are the problems, you need to replace them. Also it won’t hurt to change your spark plugs too, when you change the oxygen sensor.
I have that problem before, the oxygen are expensive to buy. But if you change them you will get better gas mileage.