On Thu, 12 Feb 2009 23:28:43 -0600, Don Foreman
wrote:

He
said it might be ignition wires. Why, yes it might indeed! Now
he's thinking like a mechanic and diagnostician rather than a computer
operator rotely going thru a checklist. It could also be a fouled
or cracked plug or distributor cap but they'd replaced the plugs and
I'm not sure engines even have distributor caps anymore. It takes
more pop to fire a plug under low vacuum (higher in-cylinder pressure)
so weak wires may spark to ground rather than fire the plug -- and
those wires are 14 years old.


Assuming the sparks come from three dry potted coils with each coil shared
between 2 cylinders, there is a non-trivial chance that one coil has a crack
in the insulation. A plug chop would identify the culprit.

Mark Rand(long tale of woe on GM/Vauxhall/Opel V6)
RTFM