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Old 12-04-2006, 08:53 AM
Warren Trafton Warren Trafton is offline
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The right spark plug?

Last summer, I decided to try the Champion RJ12YC plugs that burn hotter and penetrate deeper into the head. The hope was that these plugs would burn more efficiently with less fouling in a cool running A-4. However, there was actually a lose of power. When I pulled off one wire at a time while the engine was operating it became apparent that #3 was not firing accept intermittently. I then swapped wires but no change. I placed the plug in other cylinders and it was clear that the problem was that plug. Then, just as I was placing the wire on the top of the plug and causing it to arc, the plug would work and the cylinder would fire happily as long as I held the wire just off the top of the plug. When the wire was properly in place - no firing. When that RJ12YC was replaced with an RJ8C the engine ran great with lots of power. So, I got another RJ12YC plug to replace the one that was apparently bad. When installed, it fired normally in #3 but the plug in #1 would fire only intermittently. I came to the conclusion that with four RJ12YC's installed there was an incompatibility with my coil, or condenser, or something. I put the set of RJ8C's back in the engine and enjoyed great power with no more problems.

I would appreciate any comments as to what was going on. And I want to alert others who may be tempted to experiment with the RJ12YC's.
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