I am just not getting anywhere with the rough-idle-when-cold and related problems on my 1973 280C. Here are the facts:

- rebuilt SB and head, approx 500 miles
- valves adjusted
- points, plugs, wires new
- old plugs looked OK
- dwell steady
- timing at ~12 BTDC with vacuum at idle, appears to have normal advance as RPM's increase
- 4A1 carb rebuilt by good shop by PO
- carb adusted (idle mix, choke gap and fast idle speed)
- all smog lines connected
- EGR valve removed and manifold connection plugged
- secondaries work
- original CD ignition
- can't find a vacuum leak
- thermostat working

Here are the symptoms:

- starts instantly
- idles very rough, as in will not run below 2K RPM after starting.
- misses at low RPM driving when cold
- gradually gets better as warms up but not smooth until past 175 on the guage
- slight backfire on light acceleration when cold
- slightly rough idle even when warm
- slight hesitation/miss under light load even when warm
- slight surging at low load - like coasting to a stop - when warm

I have exhausted my knowledge and diagnostic equipment. On different days I think it is the carb, a vacuum leak, or ignition or all three.

The techs in the area are all over the place in terms of where they would start with it

Ideas, suggestions?

TIA

__________________
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