Jeep Cherokee Tune Up

Jeep Cherokee Tune Up

Jennifer’s XJ has been running a bit rough lately. We decided to try a tune up to see if the engine performance would improve. The spark plugs and wires on her engine were on the engine when we swapped it in a few years ago so we did not know how old they were.

We obtained a Tune Up kit from Crown Automotive. The kit contained wires, Champion Spark Plugs, a Distributor cap, a rotor, a fuel filter, an oil filter and an air filter. We elected to hold the filter changes for later and just do the ignition parts swap.

We began by marking the new distributor cap with the plug number for each terminal. Next we sat at the kitchen table and set the gap on all the new plugs to 0.035 using my Jacobs gapping tool. I sometimes run a larger gap but for this engine I decided to just go with the factory specs.

Next I removed the plug wires. This task proved very difficult as they seemed seized to the tops of the plugs. Even with my plug wire removal tool, several wires broke before separating from the top of the old plugs. With the wires removed, I used a 5/8 spark plug socket to remove the old plugs. I carefully cleaned the area around each hole and inserted new plugs. I ran them down until the sealing washer hit and then turned then an extra quarter turn.

The old spark plugs were the proper tan color indicating that the mixture was correct. However, they did show a great deal of wear on the tips.

Next I removed the old distributor cap by loosening the two Phillips head screws that hold it to the distributor. I left the old wires in place. I then installed the new cap and tightened the bolts.

The old distributor cap showed signs of severe pitting on the internal terminals. There was also some evidence of cross tracking inside the cap.

Jennifer carefully selected the matching wire for each plug from the kit and installed it on the appropriate terminal on the cap and then routed it to the plug as marked on the cap. She set the wires in the holders and then replaced the coil wire.

When she started up the engine, we immediately noticed that it ran much smoother. Hopefully there will be a corresponding increase in fuel economy as well.

Note that we did not install the rotor from the kit. When I ordered the kit, I forgot that she was running a 96 model distributor in her 1992 model Jeep. The cap is the same but the rotor is not. We will source a rotor separately and install it later.