500SL rough idle
 

Having rough idle trouble on a 92 500SL. Changed plugs and resistors, checked for fuel and vacuum leaks, replaced o2 sensor.
Duty cycle at 50% at start up, then increases to 93% after warmup. ASR light comes on intermittenly. I also set a code 18 when I unplugged the idle air valve( How do I reset?) The roughness can also be felt when I increase engine rpm's. Any suggestions are certainly appreciated. Thanks....

Did you check to see if the fuel filter has been replaced? Since your car is a '92, the fuel filter is 10 years old and may have junk in the fuel line. Worth a try.

Thanks for you reply. New filter didn't help the idle and the check engine light is still on. I tried to clear the code by holding the LED button down for 12 seconds with the key on engine off but it won't clear. Any more suggestions???

See if you can "read" the code. If the check engine light is on it has one. The only thing other than a worn O2 sensor that has ever turned mine on was a plugged egr line. When was the last time the plugs/wire connectors have been changed?

Plugs and resistors have been changed, new O2 sensor, fuel filter, Both coils ohm the same, EHA amp draw ok, temp sensor OHM ok, no codes showing, and still runs rough. Even runs rough at 2500 rpms. Duty cycle at 85% after warmup. Plan to check dist. caps in the morning. Any body have any other suggestions? (both coils ohm 835 on + and - connectors to the coil towers. Should these be equal?
Thanks... Larry

Just throwing this out:

Throttle Actuator?