Originally Posted by racerdad2
180k on the clock. Been running perfectly. Engine started to stumble badly cruising at highway speeds. Slowed down to accelerate thru the gears at wot & has major miss / stutter / stumble. No CEL. Where do I start looking ? Thx !
When my ignition coil went bad, the car would idle ok and drive perfectly at low load. On the highway or under acceleration, the car would occasionally miss/stumble/stutter. My car threw no CEL either, even with a pretty bad intermittent misfire while accelerating. Just throwing this out there, as your symptoms sound a lot like how my car acted. Mine was an 01, and I think you have one coil per plug instead of one master coil like I do. Don't quote me on this, but I think so. Ignition coil failures are pretty common on the earlier Foci from what I can gather, not sure about your later car. Someone smarter than me might chime in on that.
Check the obvious small things. Plug wires, ground connections, stuff like that. I'd probably pull the spark plugs and eyeball them. See if one of them looks different than the others. Look for clues like that. Probably either ignition related or fuel related possibly. How does the car drive under low load conditions, as in just cruising around a residential neighborhood? Start ok or hard? Problems worse when cold or warm?