If its EFI ganyan talaga yan. This is because it will bring the engine to STP (standard operating temperature and pressure) in the soonest possible time. Normal yan. Let it idle for 1-2 minutes.

It might also be that you need a tune-up / change-oil already. Happens to me everytime my cars near the 5000km servicing.

WD-40 is OK. Mangangamoy lang engine bay mo but no sparks. I do it palagi. ;)