I have a 2003 Ford Focus ZTS with 90K miles. Complete tune up, plugs, plug wires, fuel system flush, tranny service, all filters replaced.

My problem is when you turn the interior fan on the engine runs rough, it does not matter if the AC is on or off, though it does seem to be more prolific when the AC is on, but it will only do it when the interior fan is on?

Also I have a burnt smell from under the hood, not sure if I have an electrical issue, maybe a burnt wire.

Visual scan of the motor shows nothing obvious. A local parts store ran a scan and said I had a miss on #1 but he cleared it and we turned the fan off and it did not return.

With the fan off the car runs great.

Any help or suggestions would be greatly appreciated. Thanks