On Mon, 30 Aug 2010 00:34:04 -0500, Jon Elson wrote:



The rear plugs are a total bear on this car, but the internet helped me
find out you take the cowl panel with the
windshield wiper mechanism out to get access to the rear bank of the
engine. One plug of the rear bank
had the ground electrode bent all the way against the center electrode.
I don't THINK I manhandled it enough
to do that getting the plug out of the well and past the intake
manifold, but I can't be absolutely sure of that.
Obviously, the plug wasn't like that before the misbehavior, could a
severe knock do that to a plug? Could a chunk
of carbon have come off the piston and crunched the plug electrode? It
was bent, but not totally smashed.

This car has no distributor, and has 3 spark coils. So, each coil
serves two cylinders. What happens if one plug
is shorted? Does that short out the other plug, too? Was the other
cylinder missing intermittently, as the coil
barely had enough current to make a weak spark with one plug shorted?
The shorted plug was on the branch
with the long plug wire, the coils are on top of the front bank plugs.



If that plug was wet with fuel or fouled when you took it out then it could
have been pre-existing. If the insulator looked similar to the other plugs,
then it happened as you took it out.

The most likely cause for getting a miss starting on one cylinder after a bit
of hard acceleration, that then comes and goes, is that the insulation has
broken down on one of the three coils. If you can access the coils and inspect
them _very_ closely, you may see a small burned spot. Or you may not :-(

It'll probably only affect one cylinder, even though they are shared coils,
this is because the coils are double ended, not parallel connections.

A coil swap is usually quicker than a plug swap on these modern engines :-|


HTH

Mark Rand
RTFM