The problem areas and symptoms I have seen (and experienced) -

Warm-up regulator. Hard start, poor warmup. Usually clogged intake screen.

Idle control relay and/or idle control valve. Erratic idle. Clogged or sticking valve and/or bad idle relay.

Idle mixture, oxygen sensor, misadjusted CO. Poor idle, hard start, dies, runs rich.

Clogged tank screen. Stumbling on acceleration, may die but restart after sitting.

Massive vacuum leak due to cracks in air guide housing. Poor idle, lack of acceleration, backfire.

Leaking injector seals. High or lumpy idle.

Brightness control rheostat. No dash lights.

HVAC control (control unit(s), vacuum pods, switches). No AC or heat, uncontrolled heat, no heat to floor, etc.

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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