YJ Fuel Injection Performance Kit

K&N Fuel Injection Performance KitThe box said “horsepower guaranteed”.  And, more important, it was CARB approved.  Finally, an air intake system for the pre-1997 Jeep Wrangler that was certified as emissions legal in California.  The air intake kit was K&N Fuel Injection Performance Kit for the 1991-1995 Jeep Wrangler with the 4.0L engine.

Murphy (if anything can go wrong, it will go wrong) and I are old acquaintances. I figured I had an afternoon and a Jeep (Just Enough Extra Parts).  Time to find some more horsepower.

I opened the box and did a quick inventory of contents.  Everything appeared to be included.  The first order of business was to remove the existing air intake box.  That was simple as three spring clips held the box in place.  That left removing the crank case vent hose, evaporation canister hose and the throttle body hose the last things holding the stock air intake box in place.  Below left is a picture of the stock air intake configuration.

94 Wrangler Stock Air Intake94 Wrangler Air Intake Removed

Once the stock air intake box was out of the way, it became apparent a little cleaning was in order.  After all, it is a jeep and it does spend some time on dusty roads.  The cleaning involved a little work with carb cleaner to remove accumulated dust and grime build up where the air intake hose joins the throttle body.  Above right is a picture with the stock air intake removed.FIPK Heat Shield Installed
Now I am up to step 10 on the provided instruction sheet.  Time to install the heat shield in the former location of the stock air intake box.  The instructions and reality do not coincide.  The instructions called for securing “rubber mounting inserts” to the heat shield and then placing the heat shield in place.

I found the placing the rubber mounting inserts in the stock air cleaner locating holes before placing the heat shield in position was easier.  And, the instructions did not mention anything about the the front c-clip to firewall support rod being in the way.  Simple enough deviation; loosen rod, insert heat shield, replace rod and tighten bolts.  At right is a picture of the heat shield installed.  Note the support rod above the heat shield.

However, once the heat shield was in place, another instruction deviation became apparent.  An “L” bracket is supplied that is to firmly support the heat shield to the fender.  It does have a pre-drilled hole on the heat shield.  The instructions call for drilling a 1/4 inch hole in the fender and bolting the “L” bracket to the heat shield and fender.

That posed a problem as with my ’94 Wrangler, the power brake setup was occupying the space where the “L” bracket was supposed to be placed requiring the heat shield mounting hole be moved about an inch forward.  And, rather than mounting on the outside of the heat shield, the “L” bracket needed to be mounted on the inside of the heat shield.

To this point, the installation was straight-forward with little time spent.  After the heat shield, air intake tube and saddle bracket are in place, the final efforts revolve around connecting the crank case vent hose and evaporation canister hose.

Heat Shield and Air Intake Tube in positionHose Connections

A section of silicone hose is provided.  However, it appears as an additional hose is necessary.  In my case, I have  a Jeep (Just Enough Extra Parts) laying around.  To connect the evaporation canister, I used about a five inch section of 3/8 inch OD emission/fuel hose and a 2 1/2 inch section of the provided silicone hose.  The 3/8 inch OD hose mated to the existing evaporation canister hose and the silicone hose section provided a press-fit connection to the nipple on the air intake tube.Finished FIPK Installation

Next was the air intake tube to crank case hose connection.  The hose provided was too short to make the connection without an air flow restriction kink in the hose.  Again, the 3/8 inch OD emission/fuel hose, a 9 inch section along with the remaining provided silicone hose, was used to form a loop with no restrictive bends.  Note the positioning of the hoses in the pictures above right and at right.

After a double check to ensure all bolts were tight and no tools in the way, it was time for air leak test.  The engine fire immediately and no air leaks were detected. It is ready for a trail test to see if the “horsepower guaranteed” statement is true.

In reality, a 8 HP gain is advertised.  Without a dynamometer test, the horsepower increase may not be noticed.  However, the replacement air filter does provide for increased air flow into the engine combustion chamber.  That increased air flow intake does lead to performance gains.  The expectation is that improved idle/off idle performance with be realized.

Larger images are available in the Galleries under Jeep Tech.

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