I have a 2000 Ford Focus with new battery and cables, new alternator, less than 100,000 (barely). recently made a trip from austin to dallas and back. on the way back, on the interstate, car suddenly refused to continue acceleration (no indicator lights came on); pulled to the shoulder, shut everything off; waited about five minutes, car started up on first try…continued driving; about 12 miles later, same thing occurred. pulled over, turned everything off, started up again just fine, drove the rest of the way home. took it to my mechanic, he ran diagnostics…found nothing. Ran perfectly on short drives around town for three weeks; three weeks later, another road trip…did not run air conditioner or anything extra on the drive; about 30 miles from final destination, same thing…lost speed, wouldnt accelerate, pulled over, shut it off…started right up again and ran fine to final desitnation. On the way home, about 100 miles into return trip, same thing… lost acceleration etc. but this time would only keep running correctly for about 20 or so miles each time. was happening so frequently, had it towed home. got home, started right up, drove fine. the only thing my mechanic noted on last inspection was the AC would not turn off. could this be an electrical or switch problem? thank you for your replies 
You’re going to need to elaborate on “refused to continue acceleration” and “lost acceleration” etc. That can mean several different things all of which would be different kinds of problems.
Is this an automatic or manual transmission?
When it loses acceleration, does the engine rev up and sound just fine, but as you rev up the engine it just doesn’t feel like power is making it to the wheels?
Or does it seem to start to run really rough where the engine is spitting and sputtering?
Or does it seem like its “bogging down” - you’re revving it, it seems like the engine “wants” to rev up but maybe feels like something is holding it back or something. (Hard to describe that one).
Or does the car just suddenly seems to lose all response to the accelerator pedal? I.e. you push the pedal and nothing happens - it just coasts?
There has never been a check engine light through all of this?
hi cig, thanks for your reply
it is an automatic.
it feels almost like when your alternator goes out and the car experiences that “Close Encounters” sort of feeling, except it continues to steer fine, no lights come on, etc. When the situation starts, the car seems to shudder a bit, no noise, no lights come on…the acceleration just dies, when i pump the pedal, no response, just continues to slow down. its more as you described in your response…car suddenly seems to lose all response to the accelerator pedal, and it goes into coast mode.
no engine lights, ever come on when this happens.
It made me think of a possible wire, electric problem that only occurs at highway speeds…
i would think possibly fuel pump or clogged lines…but other than these highway incidents, it runs fine.
anddddd…it turned out to be…fuel filter
Before i went to my mechanic, i did a search of the problem on the net, using the car talk site and a few other Ford/Focus related sites. For my car’s problem fuel filter, accelerator sensor, and other sensors were the most commonly found solutions to the problem.
I was going to say do a tune up and don’t forget the fuel filter as they are VERY often overlooked during tune up time… Glad to hear you figured it out…Nice work.
I was also going to ask you to report on how it ran when it was acting up instead of shutting it down…we all on here would have probably asked you the same question on how it ran/behaved when it produced the symptoms…ANYWHO…keep on motoring. Nice to hear the actual solution…You have no idea how often we try to diagnose an issue and make tons of great recommendations…Only to hear ABSOLUTELY NOTHING in the end… People rarely tell us what happened…they just brow beat us with questions…I really don’t know why that is actually… Still trying to figure that one out
Blackbird