By 1989, the GMC Jimmy had refined its full-size, truck-based SUV formula, but that doesn’t mean they’re problem-free today. If yours still has the original fuel injection system, checking for vacuum leaks, clogged injectors, and a worn fuel pump can make a world of difference in performance. And don’t forget the weatherstripping—if it’s cracked, expect wind noise, leaks, and a drafty cabin. If your four-wheel-drive system isn’t engaging, you might have a bad transfer case actuator or vacuum switch—a common failure on these trucks. And if your brakes feel weak, check for a worn-out booster or master cylinder. Classic Parts Pro will have everything you need soon—sign up for the newsletter to get notified when parts arrive!