I have a 1998 ML320 with 100,000 miles on it. The check engine light came on recently. I took it to a mechanic and he read the code and said there are several instances of engine misfires howver he was not sure if that was causing the check engine light to come on.
He changed the spark plugs and air filter. I also recently replaced one o2 sensor.
Now my truck is running badly, when idling it is really rough, sometimes there is a rattling sound that seems to come from under the car and the check engine light is still on. The mechanic thinks the rattling might be because of the catalytic converter or fuel pressure?? He says at this point he is just guessing because he cannot tell for sure what the problem is. I don't want to keep paying for useless repairs. It is getting really expensive. Any suggestions?