I have same year car Ford KA 1999
I took it to a friend who used his engine diagnostic machine and checked for error codes etc then reset. You can buy the engine diagnostic machines on eBay for £30 - £40, i did and now check every 3 months for engine management problems also comes with disc to install on computer to check error codes if any is found.
Its been grate since. sometimes something with the computer chips change and needs resetting.
Also Idle Control Valve remove (unscrew 2 bolts) clean and put back on. Buy the Haynes Manual its a life saver. I am a novice and since buying the Haynes book i have managed to service my own car :)
Worth Every Penny
Mat
September 2008