A minor but persistent (year-long) rough idle on my 1991 240 has quickly turned into a Cold Start Nightmare over the past month:
SITTING HOURS OVERNIGHT (50 to 60-degree temp. overnight) - When I attempt to start in the morning, the engine idles high for 3-5 seconds and then immediately dies. To successfully start, I must keep pressing the accelerator pedal at least half-way down for 2-3 minutes. The engine sputters, almost backfires, shakes, lopes, almost dies, etc. After 2-3 minutes, everything runs just fine.
WARM ENGINE SITTING - Once the engine is warmed up, it will consistently start withouth problems. Still a slightly rough idle, but OK. The car does not die.
I have changed the battery, coolant temp. sensor, and spark plug wires. Any suggestions would be greatly appreciated.