[DMCForum] Samuel's Lean Mixture

["content22207" <brobertson@xxxxxxxxxxxx>]

Samuel may well have been running too lean, but I suspect it was the
CO screw misadjusted in an attempt to get the idle speed down with the
idle speed motor stuck fully open. He may have been too lean across
the board. Bet his engine ran hot as a fire cracker.

*THAT'S* why I think every owner should know how to idle their car
manually -- for diagnoses if nothing else.

Remember Ray Troxel's car at Pigeon Forge? In the parking lot of the
convention center we bypassed his idle speed motor in lieu of the
brass manifold screws. That's the same basic effect as an idle speed
motor stuck PARTIALLY open (less than 3/4").

Samuel could have a hidden vacuum leak, but that generally causes the
car to run too rich (is adjusted too rich to compensate for the leak
while idling, which then kills you at throttle). A vacuum leak AFTER
proper adjustment will cause a lean condition, such as a vacuum hose
slipping off a nipple on the road.

Re: idle speed micro switch -- purpose may have been to preserve the
life of the idle speed motor. My Renault engine came with one
retrofitted, hard wired premanently active (no place on the fuel/air
mixture unit for a microswitch). Was energized all the time. Died soon
thereafter.

Bill Robertson
#5939

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