In the 2004 model year, Nissan made the leap into the competitive, yet profitable, full-size pickup truck market. Its entry was the 5.6-liter Titan, and with a name like that, Nissan was certainly making the decision. The 2006 Titan came equipped with the same 305-horsepower 5.6-liter V-8 engine as its debut model and this engine, like all internal combustion engines, requires a specific amount of fuel pressure to operate. correctly. Low fuel pressure can cause rough idling, misfires, reduced power, or can cause the vehicle to not run at all. Checking the fuel pressure requires a special set of pressure gauges and a fuel line disconnect tool that you can rent from a nearby auto parts store.