Quote:
Originally Posted by marsheng
Plugs have the easiest time at low RPM. Although the CR may be quoted at 11:1 at low throttle openings the actual CR is much lower. Plugs fail at higher RPM and high throttle openings when the actual CR is higher and therefor more compressed air/fuel between the plug gap making it harder to jump the gap.
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This is one reason I love this forum...being wrong, for only then do I learn something.
I should state that I'm not a mechanic (more of a home tinkerer), and the opinion I offered was based on other combustion engines (lawn mowers, etc) I've worked with that have a stutter at idle and I've found dirty/fouled plugs to be an issue. I'm not doubting your statement, but it would seem to me that the "misfire rate" at low RPMs would make a stutter much more pronounced, versus at a high RPM where the occasional misfire wouldn't be as detectable, or at least audibly. Again, I actually enjoy being wrong, so if you would be so kind as to offer a "Googleable" (LOL) starting point, I can start my education.
Actually (after re-re-rereading your post), it start to makes sense regarding density and gap as related to plug failure (or at least firing), but to me it still seems that once a plug had started the failure process that it would be most detectable at low RPM even though the CR is much lower. Grrrrrr.
Also, FWIW, (as stated in a previous post) I've also had an issue with a vehicle that had a misfire that plug leads were responsible for....changing them out solved my issue.
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