Rusty’s XJ Intake and K&N Air filter Installation
	Category:	Performance
	Author:	MachineMan
	Date:	April 7th, 2005

This write up explains how to install a Rusty’s Offroad air intake, K&N air filter, and custom heat shield. Installation is based off a 1990 Jeep Cherokee 4.0L (Renix) 4x4. The installation of Rusty’s intake for ‘91+ vehicles will be almost the same with some minor differences in emission hose connections. Disclaimer – Depending or your vehicle year and local smog law’s the installation of this intake device may cause you to fail visual inspection because of the elimination of the thermostatic hot air bypass on the stock air box. The stock parts can easily be put back on if needed.

Thermostatic air cleaner

Parts
There aren’t many aftermarket intake accessories for pre ’91 XJ’s so I opted to go with the Rusty’s off-road intake system (XJAT – 1) which was only $30. Rusty’s also has two filter options; a regular 4.5x5 inch (RE-910, $30) or larger 6x9inch (RE-810, $43) K&N filer, both will work. Other than Rusty’s, Cherokee’s ’91 and up have several other intake options available made by Airaid, K&N, Accurate power, etc.

Rusty's intake kit with 6x9 filter

Installation (2 hours)

1. First you must remove all the stock parts that you won’t need for the new intake. It’s a good idea to keep them incase you need them for later smog inspections where applicable.


2. Start by removing the stock air box. Remove the air filter and bolts in the bottom of the air box, save the bolts and nuts. Disconnect the large 2 airlines and the small vacuum line that goes to the intake manifold. You can leave the small vacuum line that attaches from the bi-metal temp sensor to the Thermostatic Air intake valve.



Stock air box

3. Completely remove the Air/Vacuum multi-line disconnect. You won’t need it anymore.



Air-Vacuum multi-line disconnect

4. Now you can start cleaning up the remaining vacuum and air lines. You will have to re-route the small EGR solenoid vacuum line to bypass that multi-line disconnect. Cap one of the manifold vacuum ports that controlled the thermostatic valve. Newer models don’t have an EGR valve or EGR solenoid but if yours does than it’s a good idea to also replace those vacuum lines with some new rubber.


5. Cut the large crankcase fresh air tube on the valve cover side of the disconnect. You will need to add some rubber air hose to it to connect to the new intake. Same goes for the evaporator canister large airline, it will also need some trimming and extra hose. It should start looking like this.



Stock airbox removed and airlines modified


Modified vacuum and airlines

6. Now install the Rusty’s intake tube using the back air box stud and nut. Don’t tighten it until you have inserted it into the stock throttle body intake tube. Put the air filter on and tighten everything up and your done.



Intake and filter installed

7. Here’s a basic inline-6 vacuum air diagram incase you loose track of where stuff goes. Later models may be different and might not have an EGR valve and solenoid. Also other countries have different standards so things may also be differ like the fuel evaporative canister.



Air and vacuum hose diagram (Inline 6).

Custom Air Heat Shield (Optional)
The air in the engine compartment will tend to be hotter then the fresh outside air. Having the exhaust manifold nearby doesn’t help either. Cooler intake air can generate a bit more HP. I bent up some sheet aluminum to help reduce the hot exhaust manifold air from reaching the intake. Fresh air is still allowed to pass through the opening behind the headlamp where the stock air box pulled from. Its not optimum but should help reduce the inlet temps slightly.
For the design, your on you own. I took it in and out several times to refine the bends and cuts. It’s bolted to the chassis using the stock air box mount holes.


Custom heat shield


Intake and heatsheild installed

Testing
I like the clean look of the intake as well as the more throaty sound that comes from under the hood. There’s a noticeable whistling noise when at ¼ throttle or less which took a few drives to get used to but it’s really not that bad. Throttle response does feel a little more crisp and I did gain 1 extra mpg which made the mod worth it. Cleaning up some of the old and cracked vacuum lines probably also helped as well.

Optional Intake Installation Parts
Valve cover front crankcase air in rubber elbow – HELP #47052
Rubber air hose – 15/32” ID
Rubber Vacuum hose - 7/64” ID

Other Intake Modifications
Other intake modifications could include boring the throttle body and adding a throttle body spacer. Boring the restrictive stock throttle body is said to have guaranteed HP gains where as the spacers get mixed reviews.

Links:
Parts: www.Rustysoffroad.com, www.KandN.com and Dino’s Jeep 4.0 Performance Site

Tom K. February 2005