Well those guys might be doing alot more highway than city.

 

I checked the Knock sensor but it was OK. The next step will be O2 sensors.
How to check the O2 sensors by multimeter? I would like to the wires of O2 sensors after checking the sensors.

 

If you do not want to spend the bucks for the knock sensor, replace it with a 512k ohm resistor. I have done this on my 96 max...no more knock sensor code now for over 2years and the power and MPG went back up to normal. But make sure you put premium gas in like you are suppose to! I have 190k miles..running great with no knocking.

 

are the 02 sensor hard to change?

 

....no problem with oxygen sensor socket