Mechanics

HOW TO FIND PROBLEM CAUSING SUCH HIGH HC READINGS, CAULING FAILURE OF EMISSION TESTING

1991 Mercedes Benz 500sl • 85,000 miles

Idle is rough and at 2500 rpm engine has 900 ppm HC and you can hear and feel the miss. New pluges instaled.
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Captainkirk
September 2, 2011.




You've pretty much answered your own question. HC is basically unburned fuel, usually caused by incomplete combustion and a misfire is exactly that. You need to locate and resolve the misfire issue. Look first at plugs, wires, injectors, etc.

Wrenchtech
Sep 2, 2011.
Could be an ignition misfire, lean misfire and low compression
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Tiny
Rasmataz
Sep 2, 2011.

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