C>I've got a 1999 Deville with 135,000 miles. In the last couple of weeks it
C>just started to misfire occasionally. It has new sparkplugs about 20,000
C>miles ago. Still has original plug wires which I'm suspecting... or maybe a
C>fuel injector??? Gas mileage doesn't seem to be affected.
C>Any other ideas that I may be missing?
You are on the right track; after 100Kmi the plug wires should be routinely
replaced. An easy check would be to have the engine running, and in total
darkness, spray a mist of water over the wires. You might see some miniature
lightning under the hood.
BTW, misfires generally set a DTC, and I believe you can pull them to view. Try
pressing and holding the [Off] and [Passenger Warmer] buttons on the Climate
Control panel simultaneously until all tell-tale lights in front of you
illuminate; then watch the DIC as the DTCs are displayed, current or history.
It will start with PCM. Exit by pushing in the big A/C Temp dial button, or by
turning the ignition off.