In this paper, a control design synthesis is presented for processes modeled by a first-order time-varying lag with a time-varying delay. The basis of the proposed control method is a feedforward-feedback control system in which its stability, both in continuous and discrete time domains, is first proved in the absence of the time delay. A predictive model with an adaptive horizon is then introduced to address the effect of the time-varying delay. The system’s closed-loop response is demonstrated for fueling control in lean-burn gasoline spark ignition engines with varying transport and combustion delays. The developed methodology is validated on a Ford F-150 SI lean-burn engine model with large time-varying delay in the control loop.Copyright © 2015 by ASME