My GC8 has developed (for several months now) a minor vibration noticeable both at idle and driving.
Its pretty light, but resonates through the gear stick, steering wheel, pedals .. well the whole car really. Its a pain.
I think it might be a spark issue due to other issues/symptoms going on, namely;
vibration
small backfires, but only when engine braking downhill
fuel economy dropped
faint smell of fuel (noticed by mechanic during last wof)
If that all sounds like the same issue, I'm guessing it would be spark plug, lead, or coil pack related.
I'll start by inspecting the spark plugs? What is the best way to fault test the other components?
If one of the cylinders isn't getting enough/constant spark shouldn't it be running rough, or sound like its on three cylinders??