engine skip

2001 Focus:
When driving at any speed, the engine will suddenly "skip" as though it momentarily ran out of gas/power then it will continue to run fine. Some type of "sensor" was replaced before, but the car is still doing this.
Diagnostics won't show anything, as Ford says the problem has to be there during the test???!!!???
Can't find anyone else with same problem...wondering if it could be something as simple as the fuel filter doing this....I have a 73 LTD that did this once, and I found it was the fuel filter that a piece of dirt would clog now and then...but of course, my LTD runs better than most new cars!!!

Anyone have an idea????

Crank Position Sensor. Located on engine, near the transmission, vehicle forward. Easy to replace yourself.

There's a recall out for your car to replace the Fuel Delivery Module (Fuel pump in normal speak).
You should take it to the dealer and ask them to check if it's been done or not. All they have to do to find out is run your VIN# through the Ford System. It covers the fuel pump only and they will not attempt to diagnose anything if that doesn't fix it without a diagnostic charge paid by you.

It's worth a try. Any Focus that comes in with most drivability issues are given this updated fuel pump first.

Fuel Filters are cheap , if in doubt throw it out .. , Any Idea when it was changed last ?

They probubly replaced an o2 sensor the last time you had the problum fixed. They may have replaced the upsteam sensor, bank one. The wds system we use in Canada gives a false code for the o2 sensors. I have inadvertantly changed the wrong o2 sensor, as per the diag code from our wds. If they replaced an o2 sensor, they probubly replaced the wrong one. A faulty o2 sensor will not always aet a code right away, so it will make it difficult for the tech's to pinpoint the problum.

I am having a similar problem, accompanied by other issues (gauge sweep, lights flickering). The car acts as if I am tapping and letting go of the gas pedal 4 or 5 times in a row, and then it goes back to normal. It has also done it while using cruise control. It usually only does this once or twice per trip, but it does it on every trip.
I had the fuel pump replaced last year apparently. Any other suggestions? I have had some people mention that the wheel speed sensor (which I have been told to replace due to my other issues) may fix these type of problems. Does that seem plausible?
It's nice to see someone else with similar problems...