bobsid786

HI there,
im new to all this but doing this out of a little desperation and the need to seek a second opinion.
I bought a 2nd hand fiesta 1.8d and drove it home fine. After a day or so, ive noticed that i cant push the car past 55-60. What seems to happen is that as i accelerate, there seems to be a point where the acceleration just goes, and the engine starts making a sound similar to something grinding. In addition smoke starts coming out of the exhaust. This happens predominantly at the higher speeds (the car works fine pottering around town at lower speeds - but its when i need the speed on the m'way that it goes), and most noticeable in gears 3, 4 and 5. In 5th the car will go to 55/56mph and make that noise and start to slow down, i then need to switch down to fourth to get the speed up and then back upto 5th.

Just had the car serviced (new washers put in, oil and filters,etc) and mechanic said that he found a loose throttle cable which may have been the problem and replaced it -but the problem is still there.

Does anyone have any ideas what could be going on, it'd be great to be able to tell the mechanic when i see him this week something that could point him in the right direction?

Please Please Help, this is my first fiesta!