Mileage 101 for a Jeep XJ

After removing the stock airbox and element, we unbolted the factory throttle body in favor of the modified Turbo City throttle body. The Turbo City unit has been smoothed and bored to improve the flow of air advancing into the intake manifold. This will allow air to enter more smoothly into the engine.

We placed the throttle body on top of a Turbo City throttle-body spacer. Turbo City's T.B. spacer is not as tall as others we have seen, but still does a good job of letting the air have more time to swirl into the intake ports. Turbo City makes its spacer shorter to give the owner the choice of stacking the spacers or to leave only one on if clearances are an issue. On our Jeep, there is very little room between the hood and the Rock-It air tube we're putting on. Four bolts are all it takes to remove the stock throttle body and replace it with Turbo City's T.B. spacer and throttle body. Make sure to adjust the tranny's kickdown linkage for the new throttle body. This can be done with the twist of the adjustment screw right next to the throttle body.

The MAP (manifold absolute pressure) adjuster was the only part we put on that was not going to improve fuel economy. It provides adjustability of the fuel curve, therefore allowing you to run the engine richer or leaner. The MAP adjuster plugs in to the MAP sensor's harness and has a 12-volt wire which needs to be hooked up to a switched 12-volt power source. Once that is done, you can use a voltmeter to watch the voltage reading as you adjust the fuel curve with the turn of a screw built onto the unit. We curved our unit to give us a 5-volt reading from the MAP sensor. Cherokees are set to run lean from the factory, and we were going to increase spark efficiency with the Performance Distributors ignition kit, and therefore only saw the potential for a more complete combustion.

Next to go on was the Rock-It air tube from Turbo City. This allows a lot more air to be taken in than the stock element and also takes up a lot less room than the factory airbox. A high-flow air filter with 77 square inches of filtering surface is also included.

The last thing to be added at Turbo City was its bolt-on after-cat exhaust system for '84-'01 Jeep Cherokees. The kit comes with a Magnaflow muffler and large-diameter mandrel-bent aluminized tubing. It bolts directly into place without any welding, but it might interfere with your rear spring shackles if you do not have factory units. We had Skyjacker greasable shackles and had only a millimeter of clearance in between the exhaust tube and the shackle. A hammer will fix this later, though.

With all the Turbo City engine components on, it was time to try our Firepower ignition kit we had ordered from 4WD Hardware. We started with the Screamin' Demon coil that is a direct factory replacement featuring brass terminals, which allows us to gap our spark plugs at a recommended 0.065 inch for a bigger spark and more complete burn of the fuel mixture. The coil looked easy enough to get to, but we soon found easy-looking and easy-doing were not the same things. Though it only has two bolts holding it in place, one of the bolts was very tricky to get a tool onto.

Next to go on was the distributor cap and rotor, which feature brass terminals and resist carbon tracking. The cap came off easily enough with only two screws holding it in place. We lifted the cap off, pulled out the stock rotor and replaced it with the new one, and set the distributor cap back on. Easy as that. Once done, we also took the time to buy new plugs. Performance Distributors recommends Autolite Platinum plugs gapped at 0.050, but since the nearby auto parts store was out, we opted for Bosch Platinum 2 plugs with dual tips.

The final parts to our ignition kit were the Livewire spark-plug wires. They're 10 mm in diameter and come encapsulated in a glass-braided sleeve that resists heat up to 1,400 degrees. They're also numbered for easy installation and will allow a greater-capacity surge to get through to the spark plugs.