The first vehicles to receive this engine were the Ford Explorer and Mercury Mountaineer; years later, they began production for vehicles like the Ford Ranger, Courier, Mustang, Mazda B4000, and Land Rover LR3. A rebuilt 4.0-long block that uses the bare minimum of quality parts can end up causing problems down the road. Anonymous, CA (2000 Ford Explorer Eddie Bauer 4.0-L V6) Engine Major Engine rebuild or replacement, cylinder head, head gasket, turbocharger or supercharger, timing chain or belt. The 5.0 gives you a boost of about 50 hp and 50 ft lb torque over a 4.0. There is no arguing that. Besides, the mods you listed above don't do anything. There are dyno sheets on this site that show a stock vs CAI system runs and there is no difference. The heads only flow so much, and the stock setup is adequate. I had rough running and a P0401 code indicating an EGR valve problem. There is NO separate DPFE on an '05 despite the recommendations in many forums that you replace the DPFE first. There's an EGR systems module (ESM) that incorporates a DPFE. I got the Motorcraft EGR valve (part # CX-2102) from Amazon for $101. Spark Plug Wires – While only some models and engine combinations of vehicles today come with spark plug wires (a lot are now coil-on plug), if your Explorer happens to have them, they can go bad and cause a rough idle. Here’s a great video on how to diagnose faulty plug wires with a multimeter. 2. Vacuum Leak. Use your scanner software or pressure gage and verify that the pressure is in range. '05 Aviator does not have a fuel pressure port so you need to use scanner data. Vacuum leaks. Most rough idle issues are caused by vacuum leaks. So go through the engine carefully and use whatever means necessary to find the leaks. Overall it is a good engine. I had one in an Explorer that was a 2002. The engine was good, it was the transmission that was questionable. The thing had no dipstick and you could not change the fluid. It was a sealed transmission. I don't know what Ford was thinking when they designed that one. It had plenty of power, towed a heavy Sunbird with 1. Rough Idle. When your Ford Explorer has bad fuel injectors, you may notice a rough idle. This occurs because the injectors are not providing a consistent flow of fuel, causing the engine to operate unevenly. With a fuel injector that is not properly atomizing fuel properly, your Explorer is going to have a difficult time idling. wpbcUl.