Posted by David Sherman on Saturday, July 30, 2005 at 11:09AM :
In Reply to: Need Advice posted by Dave Burns on Saturday, July 30, 2005 at 9:31AM :
If it's not the usual carb problems (stuck or mis-set float, leaky inlet valve, etc) a weak spark can cause an engine idle okay, but miss under load. Are the plugs fouled with carbon or with oil? If oil, you probably need a ring job, if carbon, it's running too rich and/or misfiring. There could be lots of causes. If some plugs are clean and some fouled, it's probably not a fuel problem as all cylinders should be getting the same fuel -- I'd look for an ignition wire or cracked dist cap in that case. If you haven't been into the carb yet, it's probably a good idea to at least take it apart, clean everything, and put a new carb kit in, making sure the float's set right. Might have to shotgun the ignition system unless you can get it on a scope while running under load. If all plugs are equally bad, it's probably not a wire or plug problem. Could be coil, condenser or ballast resistor.