Why does my RPM dip below 1 while driving then go back up.

Engine idle control is affected by the mixture of fuel versus air that comes into the engine, as well as the emissions control system. Such a fluctuation sounds like a fuel-air issue, but this must be monitored and examined when the problem is occurring to see what is going on and why. It could even be a normal thing, but it's hard to know without observing it and seeing how other components in the same area of the vehicle are operating. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops