I recently bought a Mk4 Fiesta and I've found a few problems. Firstly, the remote locking doesn't work, I checked the receiver above the rear view mirror with a multimeter and it's not getting any power. And I don't know what could be wrong with that. The previous owner seems to have cut off and removed the door switches, the ones that make the interior light go on and off, so that could be related. Also the boot release button does nothing. I've checked all the fuses and they're all fine. Is it possible that some relays are dead? Or perhaps the alarm module?
Another problem is that it won't accelerate above about 5800-6000rpm. I've only tried this in 3rd but it just stops accelerating when it gets there and I know it should go higher because a friend has exactly the same car and it does. I was thinking it might be the fuel or air filter, or perhaps something to do with ignition.