Quote:
Originally Posted by whitemerc
Soooo, i just purchased a 1979 280e. The car starts up fine but idles really high, it doesn't seem to go down after it warmed up. Could this be the aux air valve? i have not checked the timing which i will do tomorrow. i checked for vacuum leaks and the throttle linkage as well. the car also smells pretty bad of gas but there is also a huge exhaust leak! will a stuck air aux cause such a high idle? the car doesn't have a tach but im guessing its around 2500rpm. Any advice would help at this point. Thanks!
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wm:
The aux air valve (AAV) is the first suspect in the high idle situation you describe. As noted above, it is actuated mechanically by a bi-metal spring. The valve rotates to open and close; as the spring is warmed by the rising temperature of the block it rotates the valve to the closed position.
Removing the AAV and cleaning/freeing it might be considered the first step.
Quote:
Originally Posted by whitemerc
there seems to be a screw where the linkage moves the throttle plate from wide open to closed and it looks likes this screw was screwed in a couple turns. should the throttle plate (under the huge CIS plunger) be completely closed during idle?
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There is one small (~4mm) screw and a lock nut on the throttle body (not the air flow sensor plate). That is the factory set closed throttle stop screw, and if there has not been any tampering it will be sealed with a yellow compound. It functions only to set the throttle plate to a clearance of ~1.5 - 2 thousandths (.0015 - .002") of an inch from the bore.
Near the throttle body, and closer to the block is an air bypass screw that adjusts the slow idle speed after the AAV is closed. The head of that screw is ~1/2 - 5/8" in diameter and is spring loaded to hold its position.
11-27-2016, 03:49 PM
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