I've got a 73 450sl that I just "tuned up" with new points, rotor, cap, plugs, plug wires, and air filter. I also took the opportunity to replace a lot of the vacuum lines. I also dumped a can of Sea Foam down the crankcase to clean it. All of that stuff went ok. The main reason for the tuneup was the engine was missing and idling very rough and very fast - about 1400 rpm even after warm up. I did find a broken sparkplug which caused the misfires and rough idle, but Icouldn't bring the idle down no matter what I did. It doesn't appear to have any visible air leaks. After all was said and done, I noticed the idiot engine light was now on. I haven't had this car long although it's been in the family since new. I would appreciate any help in determining how to locate the problem. What can turn the engine light on in a 73? Is it only an O2 sensor? I have a service manual, but Benz didn't put in any diagnostic or troubleshooting information into it. For that matter, I really can't find if there's any service codes, etc to read. Thanks in advance.