I've had my little 4banger as my daily driver for about 5 years now, it's got over 190k on the Odometer, and still running strong. After trying a variety of bolt-on bits, the only things that have made a noticeable difference to me were:
A) when I started using the K&N air filter (not the cold-air intake, just the slip-in)
B) replaced both my cat and muffler (nothing performance oriented, but depending on how old the vehicle is, there's a good chance the cat and/or muffler might be partially clogged and not operating at optimum efficiency)
C) started using seafoam motor treatment once a year or so (I have over 190k on mine, so I decided it's a small price to pay if this will help keep it running longer)
D) cleaning out my throttle body every year or so (also might as well clean the air ducting)
E) replacing spark plugs, wires, and distributor cap/rotor (every 12-15k)
Re-gearing is great if you can find some gears relatively cheap and have the know-how, but other than that, unless you want to drop hundreds of dollars on engine mods, just keep up with maintenance, and start saving money for a bigger engine
[B][COLOR="Red"]'97 TJ daily driver since 2004[/COLOR][/B]
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Both the 4 and 6 cylinders are long running designs. The only way you'll get more power is serious upgrades/swaps. Been numerous threads about testing common "power mods" that gave nothing. Throttle body spacers, cold air intakes, K&N filters, performance chips, removing the catalytic converter (illegal btw): all give little to no noticable increase.
I think i read a post in the engine section where the guy got 2 more horsepower after half of those mods.
EverydayTJ is right, general maintenance and upkeep will help if its been let go. I would argue the benefit of the K&N though. When i had the slip in filter I noticed a fine dust building up inside the intake duct. I swapped back to paper and the buildup isn't occuring again. That dirt buildup can shorten an engine's life.
x2 on the tune up: new plugs, dist cap, rotor, and injector cleaner made a big difference.
The main thing, though is to get used to using the gears. The 4 cyl seems to bog easily, so keep the RPM's up. It really likes 3,000 to 4,000 rpm's!
Seriously man. Save yourself a bunch of money and disappointment. If it is simply a Jeep TJ you want then enjoy what you have, but if you want a TJ with power, or even a noticeable amount of more tangible power than the 4cyl currently gets, then you should sell it and get a 4.0L.
No joke. I went through all of this (Full tune up, CAI, exhaust, 4.0L TB conversion, etc. etc. etc.). NONE of it does anything that you will notice in the 4cyl man except screw with your emissions. I finally just sold it and now, after driving a 345hp Hemi around for a while, am back in the hunt for TJ and so help me GOD it will not be, no matter what price, a GD 4cyl.
Come on man, be honest. You know when you are on the highway and there is even the smallest amount of wind or long hill (even at a tiny tiny grade) you curse that 4cyl. Off-road is fine because you use the big pedal more than the skinny one. But even then, the 4cyl sounds like it is going to die a horrible death if you are forging water for more that 20 seconds.
Seriously, I tried intake, bored out TB etc etc. Just keep it stock and regular maintence. The 4.0 had more options but it is still a jeep. want more power, going to have to swap in a V8, ....................good luck...
BTW, decades of jeeps, 4 plus, all 4cyl, go figure!.....................
1998 Blue TJ, 4 Cyl., Auto (30rh), Hardtop with installed Sunroof, mostly stock.
31x10.5x15 Mud Tires, TJ Rubicon springs, Mopar Deep Trans Pan and Cooler
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