Hi guys, new here( although not new owning ford cars). I have a fusion 1.4 duratec from 2003. I recently bought it. It has a rough idle, but I can't solve it. I can see the needle fluctuating around 750rpm. It only does this when idling, it does accelerate fine without hiccups and runs well. The problem doesn't happen always and I can't find anything that causes it. I have already changed the sparkplugs, air filter, cleaned the MAF sensor and the throttlebody. I am unsure what to try next. I thought maybe the MAF sensor is broken. What puzzles me is that it doesn't do it always. 

You seem to have tried most things, and assume you don't have access to a code reader.

Does it have a pressure switch on the steering rack? I had something similar on a Fiesta, and it was that switch.

I do have a code reader. It has no codes. Unfortunately I don't know how to read the information/data from sensors and so on. If anyone can suggest a tutorial, I would be thankful. I will check that switch today. I am also assuming at this point it could be something with the power steering. I noticed that when I am idling and move the steering wheel, the rpm drops significantly for a moment. There also was always a whining sound when accelerating. I am thinking at this point it might be the power steering pump and that the whining noise is an indication of that. 

IIRC the pressure switch is there to up the idling speed when steering lock is applied.  In my case a damaged core of the cable was causing the switch to be intermittent.

I see. Turns out the whining noise somehow is now gone. But it wasn't there while turning, it was while accelerating. I have this car only since 2 months. And honestly I only had one car before this one ( 97 escort 1.8td). Is it normal on this engine for the rpm to go down while turning the wheel stationary? I am now a bit unsure if it is something to do with the power steering. Because the steering is working fine, maybe even a little to light and there are no noises while turning or any fluids coming out. 

On a 2.81 Capri, you could stall the engine with the power steering !  No ecu, just good old fashioned mechanical fuel injection, so no rpm compensation.

I would think that if the engine RPM drops whilst applying steering lock, then the ecu is not getting the signal about the steering.

Take to a mechanic who knows this engine.