had the same problem. this might be an obvious suggestion, but new plugs and wires

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1999 Ranger XLT V6 4.0 Orange
EXTERIOR:
- Black signals & Corners (not tinted) | Clear Headlights | silverstar Ultra Bulbs | Black Taillight covers | Painted Black Grille/Valance | Painted black top step on rear bumper | Painted black exhuast & aftermarket Tip | Painted black emblems | Black toolbox | Decepticon Ford badges | 20% tint

INTERIOR:
- JVC Head unit | 4 Kicker door speakers | LED white floor lights |