Engine Performance problem
1991 Mercedes Benz 300e 6 cyl Two Wheel Drive Automatic 218000 miles
I have a 1991 Mercedes 300E with over 200K miles. Last month I had an overheating problem so I replaced the thermostat and radiator cap. That seemed to fix the overheating issue, however at one point the vehicle overheated and the engine died. Since then the vehicle idles rough as though it is only firing on 5 cylinders. Yesterday I decided to check the compression to make sure a head gasket wasn't blown between cylinders since there is no water in the oil. All the cylinders were around 120 - 130 psi but when I took out the #3 spark plug, it was fouled. I replaced all of the spark plugs with NGK's (had Autolite in there) and replaced the sparkplug wires as well. The cap and rotor were both replaced about 10k miles ago and still look good. Replacing those items didn't fix anything. If I have the vehicle in park and start it up, it idles rough but if I rev the engine up to about 2500 - 3000 RPM's, it sounds like it smoothes out but not really sure. What is the possibility of a crank shaft sensor or whatever it is that advances the timing on this vehicle. Oh ya, the check engine light is on all the time now as well. How can I check the code?