I decided to take it upon myself to do a full service on my WJ instead of paying ridiculous amounts of money to take it to the dealer. Here is a list of everything I did and then my conclusions.
- Bosch Platinum Spark Plugs: 4230 (The old Champion Coppers had eroded to a gap of .047 compared to the stock .04)
- Valvoline Max Life 10w-30
- Purolator PureONE oil filter
- Royal Purple 75w-140 Synthetic in the Diffs (plus half a bottle of FM in each)
- Valvoline ATF+4 Synthetic Transmission Fluid (changed the two filters as well)
- Mopar Transfer Case Fluid
- Bored out the throttle body and cleaned it (Removed it, used the dremel to bore it out a bit, polished it up, ground down the protruding screws on the butterfly, filed down the tab sticking down at the 12 o'clock position on the intake manifold, and cleaned it up nice and good)
- Bled the brakes
- Greased up the disconnects and addco bushings
After first turning the engine over, I noticed immediately that the idle was much smoother and it seemed to be running a lot better. I decided to take it for a drive around town and on the highway. Brakes were a lot more responsive (I think I had some air in the lines), engine was much more responsive and acceleration was smoother, and last but not least, MPG went up dramatically! I went from an average of 14.5mpg to 17.1mpg!
I drove for about 45 minutes (15 around town and 30 on the freeway). The freeway was half 63mph and half 73mph. I think everything is running a lot more efficiently and the old plugs aren't burning excessive fuel anymore. I'd have to say that this is one of the best things that I have done yet to get it running better. I think I spend maybe $200 total in parts and fluids.