UART and internal clock on PIC18F4431 - c

Question

I made a programm with a PIC18F4431 on MPLABX with XC8. It sends PWM according the value which it receives on the UART (it is DMX, 250000kbits/s). This programm works, it runs with an external clock (quartz of 10MHz).
Configuration bits :
// CONFIG1H
#pragma config OSC = HSPLL // Oscillator Selection bits (HS oscillator, PLL enabled (clock frequency = 4 x FOSC1))
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
#pragma config IESO = OFF // Internal External Oscillator Switchover bit (Internal External Switchover mode disabled)
UART configuration :
void Config_UART1 (void)
{
BAUDCTLbits.BRG16 = 0; // Générateur 8 bits
SPBRG = 9; // Vitesse de transmission 250kbits/seconde
TXSTAbits.BRGH = 1; //Haute vitesse
TXSTAbits.SYNC = 0; // Asynchronous mode
RCSTAbits.SPEN = 1; // Serial port enabled
RCSTAbits.RX9 = 1; //Selects 9-bit reception
RCSTAbits.CREN = 1; // Enables receiver
}
To improve my programm, I want to work with the internal clock (8MHz). I change my configuration bits and my UART configuration ; my programm doesn't work : do you know why?
Configuration bits :
// CONFIG1H
#pragma config OSC = IRC // Oscillator Selection bits (Internal oscillator block, CLKO function on RA6 and port function on RA7)
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
#pragma config IESO = OFF // Internal External Oscillator Switchover bit (Internal External Switchover mode disabled)
Oscillator configuration :
void Config_Oscill (void)
{
OSCCONbits.IDLEN = 0b0; // Run mode enabled; CPU core is clocked in power-managed modes
OSCCONbits.IRCF = 0x7; // 8 MHz (8 MHz source drives clock directly)
OSCCONbits.SCS = 0x02; // Internal oscillator block (RC modes)
}
UART configuration :
void Config_UART1 (void)
{
BAUDCTLbits.BRG16 = 0; // Générateur 8 bits
SPBRG = 1; // Vitesse de transmission 250kbits/seconde
TXSTAbits.BRGH = 1; //Haute vitesse
TXSTAbits.SYNC = 0; // Asynchronous mode
RCSTAbits.SPEN = 1; // Serial port enabled
RCSTAbits.RX9 = 1; //Selects 9-bit reception
RCSTAbits.CREN = 1; // Enables receiver
}