I have a 2000 Focus ZX3, automatic transmission.
There are 3 things weird happens.
1. When I accelerate getting on to the freeway the rpms climb but the acceleration seems sluggish. I didnt notice this for a while as I normally ride a motorcycle so I figured it was the automatic transmission being sluggish but a friend was driving my car and pointed it out.
2. When I'm crusing with the curise control on, ever so often you flew the speed flutter slightly maybe its only a mile or 2 an hour but its is noticable.
3. When the engine is idling at around 600rpm the side mirrors vibrate. I have notice that if I shut the ac off the engine rpm goes up to about 1000rpm and the vibration goes away but as the rpm drops back to 600 the vibration starts again.
From reading hear. I've tried cleaning the mass air flow filter. I have changed the spark plugs, plug one looked a little wet around the thread and I checked the leads for cracks and resistance checks. The leads seemed ok. I also tried disconnected the hose from the erg valve to the DPFE sensor as descibed here http://www.focushacks.com/mod/Zetec_Stumble_Fix
to see if it removed the flutter at constant speed. all to no avail.
Any suggestions on what to check next would be great