the Coil on cylinder #2 died on me last week. Replaced it (along with
the plug), (well, got it replaced since I don't have the OBD2 reader to
reset the codes afterwards). is it normal for those things to die after
52,000 miles? SInce I've got 8 of these, I'm worried it could get
expensive pretty fast :)
Am I right in assuming I could've saved some money by just unplugging
the battery, or do OBD2 computers need a software reset too?
Just the rubber part. The spring will pull off too but I don't believe it's
available as a separate part. Grab the coil in one hand, the boot in the other
the coil, twist and pull.
Look closely at the rubber around the plug opening. If it's bad, there will
be a carbon track (uneven grey\black color). If not there look at the side of
boot. You may see a tiny burnt spot with a grey corona where the spark was
through to the cylinder head. If there are signs of liquid (oil\coolant) on the
the moisture contaminated the spark plug well and caused the spark to bypass the
If you know how to use an ohm meter, you can check the windings in the old
Check across the connector terminals, then from the spring contact to the metal
in the screw hole. I don't recall the spec, but they should both show continuity.
The coil could very well be bad, but I've seen the boots fail WAY more often.
I've had several vehicles with these coils and only replaced one (most miles
on anyone vehicle was 147,000). There is better than a 50/50 chance that the
actual coil was OK, and just the plug boot was bad (or the plug itself). The
plug boot is the short connecting wire between the coil and the plug. They
fail at least as often as the coils and when they fail it is difficult to
tell that failure from a coil failure. Ford has an elaborate diagnostic
procedure for this, but the amount of labor need to complete the diagnosis
is greater than the cost of just replacing the coil, boot, and plug.
Therefore most shops just replace all three anytime a miss-fire for a
particular cylinder is indicated. I always recommend replacing the plug
boots whenever you replace the plugs. They are cheap compared to replacing
even one coil, boot, and plug combination.
Just disconnecting the battery would have reset the light, but then just
waiting for a few days would have reset it as well. Once the problem was
fixed, the code would have eventually cleared when the PCM could no longer
detect the misfire.
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