Well I'll tell you, on my 2.5 I've replaced the entire exhaust system, had the stock injectors cleaned and flow tested, replaced all the sensors on the motor, and of course plugs, wires, cap, rotor, along with a clean throttle body. That little tractor motor runs as smooth as silk and as well as it possibly can. There was a bit of an increase in power when all this was done.

All those parts were replaced with stock components and the stock air intake system will flow more than enough air to feed your motor.

 

one thing I did to my '03 2.4 was cut a hole in the side air box (removable side) and insert a 3" deck plate (bought it off amazon for $10) I keep the plate off when doing city driving. I do notice a difference in power. The engine does sound louder which is a plus and there is a possitive difference in acceleration from a stop and highway speeds.

 

one thing I did to my '03 2.4 was cut a hole in the side air box (removable side) and insert a 3" deck plate (bought it off amazon for $10) I keep the plate off when doing city driving. .

Link to pics of this this mod please, or can you post one, please.

 

I've come to the conclusion that there is nothing I can do to improve the performance of the engine as it already runs well, so I'm not going to spend any money on filters etc.

When it's time to replace cat and exhaust at some point in the future, maybe I'll regret this if I find it did bog me down some : )

 

I found this to be the best solution: http://www.wranglerforum.com/f282/keep-your-4cyl-on-a-diet-2032522.html

 

Keep it light and gear it deep is the way to go on the 4 cyl engines. I found mine to be pretty weak with 3.73's and 31's, and that is with the 2.4 which has a bit more power and the 6 spd which has deeper gearing. Now with 4.88 and 31's it runs great both on and off road.

 

There's a lot of butt dyno-induced thinking by some people who read doing something like opening up the air intake can improve power so after they do so, the placebo effect makes them think it helped like they read it would.

There are some restrictive air intakes installed onto some engines. The Camaro Z28 and the Mustang 5.0 to name two in particular TJ's OE air intake however was specifically (!) designed by Jeep engineering to be 100% non-restrictive... it in fact can flow more air than the engine can pull at redline rpms and at wide-open throttle.

So other than installing a good quality air filter like made by AC-Delco, nothing can be done to the air intake system so the engine can pull in more air... it's already getting all the air it can consume at WOT and redline rpms.

Special spark plugs won't help, nor will so-called "low resistance" spark plugs or ignition wiring. The resistance purposely added to the spark plugs and wiring is there for electrical static noise suppression but because there is so little amperage drawn, there is no significant voltage drop. As it is the spark plugs get way more voltage than is required to ignite the air-fuel mixture.

A clean throttle body is always good to have. No, replacing the injectors won't help since like the air intake, they can already flow more than is usable. The computer shuts their flow off as soon as the proper air-fuel ratio is achieved.

What commonly causes the engine to not develop the same amount of power it did when the Jeep left the factory? Oversize tires. If you have installed oversize tires, the only way to restore that power loss is by regearing both axles to a lower ratio to restore the lost engine rpms. I.E. the engine turns over at a lower rpm producing less power at the same speed when larger tires have been installed.

Replacing the coil with one that produces more voltage won't help either since the OE coil already produces significantly more voltage than required to completely ignite the air-fuel mixture. Not to mention few aftermarket coils hold up like the OE coil does. I had a Screaming Demon ignition coil die out in the middle of the desert six months after installing one many years ago. Fortunately someone in my wheeling group gave me his spare OE ignition coil. The rumors claiming the OE coil's voltage drops off at high rpms are just a myth by those susceptible to the placebo effect or what their cousin's buddy said. The bottom line is that once you have enough voltage at the plugs to ignite the air fuel mixture, any additional voltage is unneeded and of no benefit. The OE coil produces more voltage than is required, it has excessive capacity just like our cooling systems do.

There's no real cheap way to improve the power out of our Jeep engines. Before Detroit had to start eking every bit of efficiency out of our engines to continue passing the EPA's and Federal requirements there were often tweaks available to boost power but those days are gone where our Jeep engines are concerned and most cars. About the only ones I'm aware of where power isn't hard to boost are on some performance engines where for some reason they installed restrictive air intakes. Fortunately or unfortunately depending on how you look at it, there's nothing easy like that available on our Wrangler TJ engines.

Of course all that is just my personal opinion.

 

Little known secret there actually is a huge limiting factor w the 2.5.... the oem motor mount brackets severely hamper performance....
Pick up any set of modern v8 brackets along with all of the supporting v8 parts and you can double your hp....


As mentioned above.... gear it right and get it LIGHT