Threshold funny thing

Moin have a Ford Sierra 91er dohc gbg now I have just entered my 2 powercaps (2farad together). after that I wanted to start driving start the engine and wonder. so before start short about 1500-1700 at the start afterwards he went very quickly to short under 1000 now (apparently through the caps) start 1500-2000 (which could be explained by the less breaking voltage) but after that he does not sink but stays at about 1800 or even goes higher (up to to 1900) after about 15-20sec it goes back to about 1100. if I pass through it when it’s high-turvy it goes up (normal) and then down to 1000 but then back to the high empty run area (unnormal) when it’s running a time it’s gone. but what is that from? does anyone know the problem?