My 300E has 201K, and I have had it for five years. It has always had a "stutter" at idle.

A couple of weeks ago it began to miss under load at low RPM, and occasionally die at idle and then be difficult to start and refuse to idle. Then it would be fine for an hour or a day. This only occurs with the engine warmed up, usually just after the temp passes the 80 degree mark.

To fix this, I did the following:

- inspected all vacuum connections - no broken, loose, or cracked connectors

- checked vacuum: steady 19-21" at idle

- replaced the spark plugs with Bosch H9DC copper

- replaced the O2 sensor and verified cycling around 50% (needed at tiny amount of richened. Cycling at idle and 2500 RPM is about the same.

- cleaned the rotor and distrirbutor cap contacts

Following this, the car was running better than any time I remember. I drove the car a couple of hundred miles with no problem. Then tonight, I drove about 3 miles and was stopped at a light. Rough idle and died. Started hard. Drove to restaurant, missing badly at low RPM and very rough idle. Ate dinner (about 90 minutes), car was fine on way home.

Cap/rotor, plug wires, fuel and air filters replaced 20K miles ago. Fuel distributor is a rebuild and looks fairly new.

Any ideas?

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe