90q missing on cyl 5...ideas?

[Orin Eman]

>
> Hello Dave............Might be a bad wire. Also, make sure your ignition
> wire from the coil is pushed down all the way in the neck of the coil. That
> connector tends to creep out in small increments, and eventually the
> weakest sparker starts cutting out, and the oxygen sensor starts seeing
> rich unburned mixture so it leans everything down

Actually, the O2 sensor doesn't understand raw fuel.  It sees all that
excess oxygen that didn't get burnt at all and signals lean,
resulting in a rich mixture for the other cylinders.  You can very
rapidly foul plugs when this happens.

and then the other
> cylinders don't run right, and the owner starts wondering if the engine
> will get him home. When you floor it, the mixture gets better and it runs
> better, but not right.

It runs better because it goes open loop and ignores the O2 sensor.
Still not right because of the misfiring cylinder of course.

Orin.