Mercedes-Benz W126 auxiliary air valve and idle control valve
280 SE280 SEL380 SE420500 SE
W126 idle is high or uneven, could the cause be the auxiliary air valve?
Yes. A dirty or stuck auxiliary air valve or idle control valve lets air pass wrongly: the revs of a warm engine stay high, the idle jerks or the engine may stall, for example at traffic lights.
Does cleaning the auxiliary air valve or control valve help?
Cleaning and lubrication can help for a while if the parts are only sticky. Sometimes cleaning makes the moving parts even stickier. The lasting fix is often a new valve, and sometimes the fault was in the other solenoid valve.
What else should be checked before replacing the valve?
Check the vacuum hoses and intake air for leaks, and the ignition timing, as they affect idle in the same way. The control valve gets its control voltage only when the engine is running; without control the engine runs at about 2000 rpm.
Related articles
Mercedes-Benz W126 heater blows only hot airMercedes-Benz W126 heater not heating or heat disappears while drivingMercedes-Benz W126 K-Jetronic cold start injectorMercedes-Benz W126 runs too rich: causes and lambda sensor checkMercedes-Benz W126 fuel pressure regulator and pressuresMercedes-Benz W126 clogged and leaking fuel injectorsMercedes-Benz W126 idle speed and high idleMercedes-Benz W126 distributor cap, rotor and spark plug wires