According to Haynes Repair Manual 1984 through 2000: Cherokee, Wagoneer, Comanche; "1. Loose or damaged wire harness connections at distributor, coil or alternator. 2. Intake manifold vacuum leaks. Make sure all mounting bolts/nuts are tight and all vacuum hoses connected to the maifold are attached properly and in good condition. 3. Insuffucuent fuel flow."