My 1997 expedition, is back firing when I am accelerating,

SOURCE: 99 Expedition - Stutters and loses power when accelerating

My was doing the same thing, it was an EGR valve and a misfire on the #2 cylinder which required a new spark plug and a coil pack
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SOURCE: misses during acceleration , rough

Go get the codes ran at auto zone or advance auto parts they will do it for free. If the codes come up as a cylinder miss-fire then it is most likely a coil (being a ford). Write down which cylinder it is. I wouldn't replace any of the spark plugs , useless you have more than 100,000 miles. If you have to replace the spark plugs use BOSH double plautim or better. The cylinder placing is ( as your are looking at the front of the truck) passenger side front to back 1-2-3-4 driving side front to back 5-6-7-8. If you never seen a coil buy one so you know what you are looking for. The coil is held in by a 7mm bolt. Take the bolt out and replace the coil. Problem Solved. Estimated time 20 Mins with 60 dollars per coil.

SOURCE: power loss and black smoke?

I had a similar issue to this after I got in a VERY small fender bender (literally) in an 87 Turbo Supra. In my case, my pasenger fender got pushed in JUST enough to crack a charge pipe and cause a boost leak.

Basically, what was happening was the turbo would spool and build boost, the mass fair flow sensor would read all this air coming in and tell the ECU to dial up the the appropriate amount of fuel. When the air reached the cracks in the charge pipe, it would escape out of them. Thus there was a much lower air-to-fuel ratio, causing less fuel to combust, which lead to power loss and black smoke out of the exhaust.

My guess is either an oxygen sensor, or more likely a boost leak.

Good luck mate.

SOURCE: Shuddering and white smoke on acceleration

Does this only happen at lower rpms, say while turbo is still at slow speeds? I have the same issue and it only has this issue when below 35mph. Once I'm in 3rd gear it never smokes no matter what. I believe the turbo is lagging pretty bad and once you get to the higher speeds the turbo is spooling pretty good and no loss of power at higher speeds. I pulled the turbo intake and it has quite a bit of oil residue in it (bad seals) Just ordered new turbo and will keep you posted when i get it installed. (Also could be throttle position sensor )

SOURCE: 2001 focus. Replaced plugs, wires and coil pack.

Have you replaced the timing belt? if not i would highly recommend doing so. these cars need to have the timing belt replaced before it breaks otherwise it can and will cause major engine damage.