2000 ford focus idles fine but has a bad vibration in the engine under acceleration?

Question

i already tried changing the plugs

Answer 1

Is it possible that a couple of plug wires could be crossed-if you changed the plugs. Or maybe timing off-if you moved the distributor a little, or spark advance unplugged check for a vacuum tube left disconnected, or plugged into the wrong place?

Answer 2

The fly wheel, or Harmonic balancer(Crankshaft pulley balancer) sounds like it's out of balance, or bent. A weight might have come off the balancer causing your engine to vibrate at certain RPM's. Kind of like when you lose a wheel weight off of your rims, You know... You drive and at certain speeds you'll feel the steering wheel vibrate, or the car shakes a little. Because the tires are not balanced.
When under the hood get someone to slowly rev up your engine, and keep an eye on the pulleys to see if any of them are bent.
The cam shaft could also be bent... You can't see that if it is.
If it shakes at Idle, You could have a bad spark plug wire or spark plug. Or if work was just done on the car, you could have wires on the wrong spark plugs. That will cause you to to feel vibration, but it will feel like it's smooth for a second, then you'll feel a shake, then smooth , and then a shake again. This feeling I'm describing happens fast. Put an inline spark tester a plug wire and look for a steady pulsing light. If it's steady and then has a noticeable gap in the blinking, your wire or spark plug may be bad. Do this to each cylinder to find the cylinder that is not firing correctly. Then change the wire or plug causing the problem.
An inline spark tester cost under $10, And can be purchased at just about any parts store

Answer 3

Beleive it or not there is a bulletine for something like this first off is the check engine light on if not check this out. in the front of the engine at the bottom is a motor mount that looks like a mini shock alot of focuses had problems with rocks and mud and junk getting stuck up in behind this mount which caused the engine to vibrate horribly when under a load the same thing happened to my friends focus you could barely hold the wheel it vibrated so bad we removed a rock that was stuck up in there and it was fine after. well hope that's all it is good luck

Answer 4

I'm afraid there is not an easy answer for this one.

Short of have a engine diagnostic done, there's not much you can do. (not just a code scan)

If you want to start replacing a bunch of parts in the hopes of finding the faulty sensor, plugged fuel filter, bad fuel pump, weak ignition coil, bad O2 sensor, faulty ignition module, ......

this list is extensive.

ADDED:
Try a new fuel filter first.