Quote:
Originally Posted by alexiskai
Isn't a contribution test used to isolate a single bad cylinder? It wouldn't really tell you if all the cylinders were equally worn.
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Actually, it generally tells quite a bit. When used in conjunction with a sensitive RPM gauge, it can help diagnose items like a worn cylinder(s), or too lean fuel mixture, or leaking manifold, etc. as it points you to the faulty areas to check mechanical items. If each cylinder dropped the RPMs by 25% when cancelled, that would indicate all 4 cylinders are pretty even. If #1 and #4 RPMs drop by 30% but #2 & #3 only drop by 20%