Big thanks to Mallcrawlin user DJJordache and the information contained in his thread, found HERE
. His thread contains the dyno data and comparisons of the older manifold vs. the new manifold. But I feel like there were a few portions that were unclear and there is a lot left to you to figure out. So I made a write up to make it easier for everyone to do this swap.
Note: This write-up is for the 1993-1998 Jeep Grand Cherokee “ZJ”. While the 4.0 was used for many years on many different vehicles, there is no gurantee the benefits and procedures listed will apply for any other vehicle equipped with the 4.0. That being said, if you have confirmed success with another vehicle such as the earlier XJs or Wranglers, please feels free to post or PM me so I can add it!
(from DJJordache on Mallcrawlin) In 1999, Jeep had to redesign many parts of the venerable four liter to meet increasingly stringent emission controls. Some of these redesigned parts of the engine were, but not limited to, smaller exhaust ports to heat the inline catalytic converters quicker (The original exhaust outlets were nothing to write home about and now are smaller), two inline catalytic converters in the exhaust manifolds (This in addition to the original, but more efficient catalytic converter in the exhaust system), revised camshaft timing to reduce overlap and duration, and revised computer timing maps. None of this is conducive to increased performance.
Jeep’s answer was to redesign the intake manifold, EXTENSIVELY, to make up for the power losses due to tightening emission regulations.
DJJordache installed the new intake on his fairly well modified 93 Grand Cherokee, including throttle body, head port & polish, valves, exhaust modifications, etc. but all of these were used in the “before” test. For changes he used newer 49psi injectors stock on a 2000 4.0, and used a fuel pressure regulator to achieve 49psi. (stock he measured at 43.5) With these changes he claims a 26.9 gain in horsepower at the rear wheels; and a torque gain of 19.7 at the rear wheels
. You can read more in his thread which is very well written as far as the tests are concerned.
Now there are some who say that that the gains from this intake manifold on a totally stock motor are not as impressive, but I have been closely paying attention to the benefits and I will keep updating with what I find:
Highway driving, cruise control off, between 65 and 75MPH (with slowdowns in towns with traffic lights and 55-35mph speed zones):
Noticed improvement in fuel efficiency by 2-3mpg from previous trips.
Highway driving, cruise control set between 70 and 75MPH
Noticed improvement in fuel efficiency by 1-2mpg
City driving (short trips with frequent stops under 50mph (torque converter not locked):
--will test soon—
City driving (shot trips with some stops between 40 and 60mph (torque converter locked):
--will test soon—
Mix of city and country road/highway driving (city situations as above, along with stretches of constant speed between 50 and 65 mph).
--will test soon—
I have noticed it has a much easier time keeping a constant speed up hills, and no longer has to kick down to third to maintain speed. It seems to have a slightly easier time driving and accelerating as well. Overall I’m quite pleased with my results.
This was performed on a 1995 ZJ Grand Cherokee, stock excluding:
Intake modification (remove grille snorkel thing, cut out front of airbox and removed restrictor)
The only change was to the new intake manifold, taken from a 99 XJ.
-You will need a bracket from Lowes or Home Depot to replace the fuel line bracket. I didn’t have access to a drill capable of drilling through metal, you can use your original bracket if desired, but I think a 62 cent metal thing is just as good. You will need an L-shaped bracket, found in the fencing section. I will explain how to install below.
-A ratchet kit with at least a 12” extension and U-joint.
-2 feet of vacuum line. I don’t remember the diameter measurement, but there is a piece of L-shaped hose I used to get the correct size from Auto Zone. I also purchased the corresponding couplings to connect the extension line to the too-short vacuum line.
-Although not necessary, you can if you prefer get a new intake/exhaust gasket.
-If you are still using stock injectors, I highly recommend you get 703 or 715 fuel injectors to take full advantage of ne new manifold. See my other write-up HERE
The following applies to 93-95 models ONLY. 96-98 do not need to modify their power steering pump or belt routing because the new manifold has the same mounting threads.
-Black bracket from the junkyard, p/n 53010148
and ALL associated nuts and bolts and idler pulley spacer (you can reuse the idler pulley under the A/C so you don’t need the actual pulley...JY pulleys tend to be rusty :P)
-New belt for 96-98 routing you will be changing to, p/n 4060922
I was able to do this without detaching the power steering lines from the pump or the steering. This is possible through some modifications and bolt usage I tried that have worked just fine.
Now I will go through the procedure for removal of the old manifold:
You should start after your engine cools off. Pull the fuel pump relay and start the engine to de-pressurize the fuel rail.
After the engine stalls, unhook the negative cable from your battery.
Remove the airbox and throttle body.
Unhook the throttle cables, unbolt the cable mount bracket and set them aside where they won’t be in the way.
Relieve the tension on your engine belt
a. For 93-95, you can remove it entirely. You will be using a different belt and new routing.
b. 96-98 can leave the belt as it is and work around it to avoid the hassle of putting it back on.
Remove your power steering pump and brackets
a. For 93-95, also remove the big aluminum metal mounting thing and all brackets.
Set the power steering pump aside where the airbox was, being sure that it won’t move and that the hoses aren’t crimped or pinched
a. If you do not want to adapt the 93-95 pump for use with the new intake and would rather use all OEM mounting, you can remove it entirely.
Unhook the electrical connectors from the fuel injectors and set them out of the way.
Unbolt your fuel rail and pull the rail back sharply to remove it, set it out of the way.
At this point, you can see my guide listed above to swap fuel injectors if you are still using stock injectors.
Remove all vacuum lines from the manifold, set them all out of the way. Vacuum routing may be slightly different on different ZJs, so snap a picture before you remove the vacuum lines just in case
Remove the fuel line bracket from the manifold and fuel line. Save the bolts and nut!
Make one last check to see if there is anything else attached to the manifold.
Now you can start unbolting the actual manifold. The best thing to do is remove all the bolts under the manifold first, then take off the top ones. Take your time and use the U-joint and extensions to help you. The last bolt removed will let the manifold fall, not a big deal if it does but it would probably be better to just catch it
With both manifolds off, start looking at what you will take from the old one to put on the new one. See this picture for what I did that worked for me:
And now you have a big empty space ready for your new manifold!
Position the new manifold. You may choose to unhook the exhaust at this point and put a new gasket in if you choose. Once you have it positioned, put one or two bolts in on the top to hold it in, then thread the rest of the bolts as far in as you can finger tighten them. Then go ahead and tighten them down
Place your fuel line bracket so that looks like this:
Make sure everything is tight so that your fuel line doesn’t have a lot of ability to move around. It might help to put the fuel rail where it will end up bolting on (but don’t bolt it down yet.)
Use the vacuum line and couplings you have to extend the vacuum lines you have to extend. Here’s a pic to show you what I did:
Put the fuel rail back on. Make absolutely sure you re-seat the injectors properly! If they do not go into the manifold all the way they will leak profusely. Bolt it down after it is seated properly. Plug all the electrical connectors back in.
Now the power steering pump. If you have a 96-98, just bolt it back up as it was and you’re all done. For 93-95, I have devised a way for it to be possible to keep your power steering pump with the new manifold:
a. First, you need to bolt the new black bracket onto the engine. The holes at the top will line up with the holes on the manifold.
b. Line up your power steering pump. As you can see from this picture, you will use a long bolt on the top left (or middle) holes, and two bolts on the top holes going in from each side. Since both the power steering pump and the manifold are threaded, you have to make absolutely sure the power steering pump is flush with the manifold.
A friend can hold the pump while you screw in the top-rear bolt, but it is possible to do it by yourself.
Once you have that bolt tightened down, you can screw in the long bolt on the middle holes. Now the first half of the bolt is threaded and will have to go all the way through. Once you reach the end of the threads it will become considerably more difficult to turn the bolt. Keep going, you won’t strip anything. If it becomes unmovable stop and make sure you aren’t actually stripping the threads on the manifold. But once you get is screwed down, it will be nice and solid.
You can now screw in the front bolt on the top holes. For the bottom holes, with 3 different threaded sockets I didn’t try to put the long bolt in (I tried on the top and it was just too difficult to turn with the three different threaded sockets, I’m afraid I probably would have stripped the bolt or the threads or both), and unfortunately the way the manifold is makes it impossible to put a bolt in the rear lower hole. So just a short bolt on the front should be sufficient.
c. After a 6hr trip and various driving, there have been absolutely no problems even with a hairline gap between the manifold and socket at the lower holes. I can’t guarantee anything, but I have had no problems and I’m satisfied with how it solid it turned out. However, if you feel more comfortable with all OEM mounting, you will need to purchase or find a 96-98 power steering pump, and bolt everything up.
Now to tighten the belt. It’s the same as usual with 96-98, but for 93-95, it means new routing and a new belt
a. You will need to remove the idler pulley from underneath the A/C. It is held in by a long bolt and nut in the rear. I found it is easiest to access from underneath.
b. Once you have the idler pulley and its washer thing, put the long bolt and nut back on because it holds up your A/C bracket.
c. Now you can take the idler pulley and thread the bolt into the belt tensioner thing on the power steering bracket.
Tighten it till it’s just barely snug.
d. Route the belt according to this diagram
e. Then you can tighten it by turning the belt tensioner bolt clockwise
f. Now there is a tension specification for the belt, but because I didn’t have the proper tool I tightened it to the tension I felt previously by pushing the belt down…maybe not the best way but still…a cheap way
Bolt down the cable mount, replace the throttle body and hook up all cables.
Put the airbox back on, and make sure all hoses and lines are in properly
Make a final check for anything that looks out of place or out of the ordinary.
Hook your battery up.
Turn your key to the ON position to pressurize the fuel rail. I had some serious fuel leakage and the fact that you will be handling and contorting the fuel rail and line around makes it very important to check for leaks before starting your engine.
Finally start your engine, check for belt travel or excessive vibration or leaks from the power steering pump (carefully! Stand out of the way in case the belt snaps from something put on wrong).
Once you see everything is operating properly, take it out for a drive and enjoy your new, upgraded intake manifold!
Feel free to post comments, corrections, and questions! I would like to make this as accurate as possible.