Stuttering at low speeds and over revving at high speeds

[DUSTY]

Hi all,

My Honda Jazz 2003 1.4 Auto has been idling strangely, stuttering at low speeds and over revving when pushing past 50mph. The engine management light has also been flickering on and off intermittently and the D symbol on the transmission has been flickering on and off.

I managed to get an OBD scanner and scanned the car and it came up with two error codes:
P1890 & P1887. If.someone could advise what needs doing now and where to source a replacement part it would be appreciated.