Jeep has used three different engines for the WJ series (plus a couple of 5-cylinder diesels for the export market):
4.0 liter I-6 (242 cu in., 195 bhp)
The standard in-line 6 cylinder engine was significantly reengineered in 1999. Upgrades included new cylinder heads with reduced-area exhaust ports, new exhaust manifolds, a new 50% more efficient slitter-vane water pump that added two horsepower, a new elastomer-coated steel intake manifold gasket, a two-piece high silicon-molybdenum alloy cast-iron exhaust manifold, automated belt tensioner and a new laminated oil pan. These refinements added more power (10 bhp), a 5db quieter operation with an enhanced lower “throaty” sound quality, and cleaner emissions.
For comprehensive 4.0 perfomance information and specifications, visit Dino’s JEEP 4.0 performance site.
4.7 liter V-8 (287 cu in., 235 bhp)
The all-new 4.7-liter V-8 engine offers more power, less weight (438 lbs), increased fuel efficiency and lower emissions than the 5.2-liter engine it replaced. An incredibly detailed tech analysis, written by Richard Ehrenberg in 1999, can be found here: Chrysler’s New Cammer.
4.7 liter V-8 HO (287 cu in., 265 bhp)
A High Output version of the 4.7L was introduced starting with the 2002 model year. The performance modifications added 30 horsepower and 30 Ft.-Lb. of additional torque. The HO engine is designed to run perfectly on standard octane fuel, but for maximum performance premium fuel is recommended.
The HO engine is standard on all 2002-2004 Overland models, and is optional on the 2002-2004 Limited 4WD models. In the 2004 model year, Jeep offered the HO as an option on three special models, the Freedom, Columbia and Rocky Mountain editions. It has not been available on the Laredo, Laredo Sport or SE (Special Edition) models. All 2002 models with the HO engine featured a nice custom chrome exhaust tip. This was, unfortunately, decontented starting with 2003 model year production.
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