YOU SAID:

the cars engine was firing a bit slow

INTO JAPANESE

車のエンジンは少し遅く発砲していました

BACK INTO ENGLISH

The car engine was firing a little late

INTO JAPANESE

車のエンジンは少し遅れて発火していました

BACK INTO ENGLISH

The car engine was igniting a little later

INTO JAPANESE

車のエンジンは少し遅れて発火していました

BACK INTO ENGLISH

The car engine was igniting a little later