300E High idle after revving and 10mpg
89 300E, mileage unknown (odometer stopped a while back), probably over 200k miles. Engine will start after 3-4 secs of cranking. Then it will run very rough. Shaking the entire car, (mounts are good). It runs very rough and hesitates while cold but once it warms up itll be very fast but still shake. So last night I decided to rev it to about 3500 rpm while it was cold and it returned to 1500 rpm instead of 700. Once i put the car into gear, it dropped down to 700 rpm. I am also getting only 10 mpg freeway w/ 91 octane. I think it is the 02 sensor but I am not sure.
To remove the spark plug, do I twist the boot a 1/4 turn and then pull.