If it's at idle clip a timing light onto the coil lead and each plug lead
and watch the flashes. If the misfire is accompanied by a missing flash
then ignition is the problem, otherwise probably carbs or possibly plugs.
But if you use a 12v timing light with inductive pickup these usually do
*not* flash on a plug lead if that plug is breaking down. Regular flashing
on the coil lead but intermittent on the plug leads indicates a bad cap or
rotor, change both. Intermittent flashing on the coil lead indicates a bad
coil or LT problem Problems with points or LT wiring usually shows up on
the tach as a dipping with the misfire. A failing condenser doesn't usually
affect the tach, and may not even cause a misfire when idling, but may under
load or make for difficult or non starting. They are cheap enough to
replace anyway, but bear in mind Hunt's Fifth Law: "'new' parts can be
faulty when you receive them; 'new' parts will sometimes fail soon after
fitting; 'new' parts almost certainly won't last as long as the originals."
PaulH.
----- Original Message -----
From: "dave houser" <mgs4dave@tampabay.rr.com>
To: <mgs@autox.team.net>
Sent: Thursday, October 09, 2003 4:19 PM
Subject: misfire
> A misfire in my 67 BGT through the idle and under load has developed and
> worsened.
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