If it's under the hood of your D90, you'll probably find something about it here. Topics are broken down somewhat like sections of a service manual. 1994 and 1995 model NAS Defenders were fitted with a 3.9 liter V8 similar to early NAS Range Rovers. These engines were fitted with ignition distributers, 3-wire O2 sensors, and individual V-type drive belts. 1997 model NAS Defenders were fitted with a 4.0 liter version of the same engine. The actual displacement change was only a few CCs, but many of engine peripherals changed more than the block itself. These later engines were fitted with distributerless ignition, OBDII diagnostics, 4-wire O2 sensors, and serpentine belts. Other peripherals like alternators also changed with different model years. When discussing engine topics, make sure you know which engine the poster is refering to, and how it may be different from yours.
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