Keeping tires, brakes, wheel bearings, U-joints, belts, and hoses in top shape will lessen the need for trailside fixes. Be certain that all fuel hoses and pipes are in top condition and out of harm's way. An unnoticed fuel leak off-pavement could quickly lead to trouble...avoid running the engine to provide work lights at night. Bring portable lamps and plenty of layered, warm clothing and blankets. If you need to stop for a while in cold weather, avoid idling the engine to keep the heater going.
Extra fuel should always be available when traveling remote trails. These days, you'll want to fill the cans at an area with reasonable fuel costs. (Fuel as high as $6 per gallon is possible in a remote or mountain community; locks on fuel cans are advisable.) Keep in mind that off-road fuel consumption is time based. If a road looks primitive on the map, make sure you know how many hours you will drive - not the distance. Be aware of your vehicle's fuel habits in low range and at crawl speeds!
 Complete Mopar EFI/MPI system...  Complete Mopar EFI/MPI system for a 4.0L six-cylinder is also the Mopar Performance platform to convert a 4.2L six-cylinder from carburetion to EFI. A variety of sensors help the engine save fuel and reduce emissions. Easy cold start, efficient warm-up, and fuel savings at normal operating temperature are some of the goals. A manifold absolute pressure (MAP) sensor knows the altitude, while the oxygen sensor(s) in the exhaust stream help keep the fuel mixture in check. |  The ignition distributor followed...  The ignition distributor followed from the breaker point and conventional electronic ignition era into the electronic fuel-and-spark management EFI era. The EFI/MPI distributor for a 4.0L Jeep inline six-cylinder was in production through 1999. EFI engines have computer controlled spark timing and a crankshaft/camshaft position sensor. Latest coil-on-plug technology eliminates the need for a distributor. EFI/MPI distributors require periodic service of the rotor, cap, and cables. Earlier carbureted engines also add breaker point service to their tune-up requirements. |  For maximum fuel efficiency,...  For maximum fuel efficiency, an oscilloscope engine analyzer (left) confirms the condition of the points or module, rotor, cap, spark plugs, and cables. Distributor strobe machine (right) from the breaker point era has been adapted to service electronic distributors as well. Spark wires can be tested simply with a volt-ohmmeter. For off-road fuel efficiency, compare ohm readings of cables to factory specifications listed in a manual. Distributor strobe machine calibrates spark timing curves for maximize efficiency. |
 Spark plug gap is critical....  Spark plug gap is critical. A parallel gapping tool assures even firing under severe driving conditions. Generally use the proper heat range plug; if your engine is carbureted, a hotter plug can compensate a bit for higher altitude. Spark timing requirements are related to atmospheric conditions, and at higher altitudes, horsepower loss can be recovered some by advancing the spark timing. As a rule, one-degree of extra advance per thousand feet of elevation works - do not exceed 7 to 8 degrees of added base timing. Return timing to its normal setting as altitude decreases, otherwise detonation (ping) will occur. |  Often overlooked in the fuel...  Often overlooked in the fuel mileage equation is compression and cylinder seal. At higher altitudes, lower manifold vacuum is the equivalent of lowering the compression. Lower compression means less fuel efficiency, poorer combustion, and a struggling engine. The cylinder leakdown tester is the best diagnostic tool for testing engine condition. There's no point in tuning an engine - and no chance of getting maximum fuel efficiency - with poor cylinder seal and low or uneven compression! |  |