One day inevitably your truck will leave you stranded. At some point some part will break causing the truck to be immobile. Well my day came this past March when my 1988 4.0 ltr. I6 engine threw a rod going down the highway leaving me four hours from home. Not much fun, let me tell you. Since then I've spent countless hours researching and even more hours wrenching trying to get my only ride back on the road. In this article I'm going to go into some of the issues you'll have to deal with to swap a newer "High Output or HO" 4.0 into a non HO truck. (Sorry I don't have any pictures)

Initially it seems as though it won't work without swapping the entire wiring harness which I DID not want to do. So I decided to look for a low mileage non-HO which is a rare piece. I finally found one that was rather cheap and agreed to purchase it from a salvage yard. When I got there they loaded me up, I paid my bill and we drove away with it. After getting it home I realized that I in fact HAD got a HO engine. Well now that I've got a newer engine than originally agreed on I wasn't going to take it back. Now I was in for more than I had originally bargained for which delayed the finishing of the project but after this article I hope to keep you on schedule.

This article is in NO way to replace a good service manual and there are steps that may have been left out because of length and my sketchy memory. This article also in NO way replaces the necessary research on your part that should accompany any swap of any parts. Also this is NOT saying that this swap or parts or installation will work just like this for EVERY vehicle. You are responsible to know what models and parts you have and will be replacing and to do the research to see if the swap is possible. Some custom fabrication MAY be necessary.

PULLING THE ENGINE:
The I-6 is relatively easy to work around and with. The easiest way to get the engine out is to separate it from the transmission and pull just the engine. You'll have to remove the power steering and air conditioning (don't disconnect the hoses, just set them aside). Also the radiator should be removed. If you are careful you will not have to remove the air conditioning condenser. The alternator and the starter also have to come off, as does the exhaust downpipe. When removing the accessories you do not need to remove the brakets, just the accessories. The next task is to chain up the engine with an engine crane capable of holding the weight of the 4.0ltr engine. The top two bellhousing bolts on my non-HO engine are TORX socket, not a torx wrench but a torx socket. Torx sockets can be bought at Sears or other places. I believe it was size E12. If took me 3 hours to get these 2 bolts out. It took several feet of socket extension bars and several u-joints. The u-joints with springs around them would have REALLY helped. After removing the engine mounts, the mounting bolts that connect the drive plate and torque convertor and the bellhousing bolts the engine can be lifted out of the truck. Make sure to mark the drive plate and bottom of the tranny side of the bellhousing so that they can be lined up correctly to keep them balanced upon installation. The engine will come out of the engine bay if pulled forward as far as possible and twisted some to squeeze it up past the firewall.

SWAPPING PARTS BETWEEN ENGINES:
There are some new updates they've made to the HO engines and these parts will not work with the non-HO computer. Also some of the accessories will not fit in the updated bracketry. The alternator and air-conditioning bracketry needs to be taken from the old engine and put onto the HO engine. (This is ONLY if you're using the old alt. and air cond.) The distributor needs to be swapped also. The old distributor must be used with the old computer. Make sure to get the distributor aligned in the proper position related to the engine stroke. Refer to a service manual for proper indexing. The ignition coil that was bolted to the passenger side of the HO engine (at least on mine it was) needs to be removed. You will use the old coil and ignition system. The powersteering bracket can be left on...it's slightly stronger and has the same mounting holes. Next the wiring for the injectors. The swap is self explanatory. My HO harness was just chopped off so I HAD to use the non-HO harness. The new HO engine will have the electric fan temperature sensor located in the thermostat housing. As of this writing I'm not sure if it it will activate the relay correctly or not. This function was handled by the HO computer. I have installed a manual switch that I flip when I'm running warm until I figure out if it will activate the relay.

Throttle Position Sensor:
The TPS on the non-HO engine has 2 connectors that come out of it. One connector (flat one) tells the computer how much throttle is being applied. The other (square) controls the TCU (transmission control unit) which controls shift points. The HO TPS only has 1 connector that goes to the computer. The computer controls the TCU. It is fairly easy to fabricate a small spacer and "widget" to allow the use of the old TPS with the new throttle body (This is a MUST) so far unless you're a rocket scientist and can rewire This is the only choice. But it's not to hard to make a little adapter. There are several ways to go about it. I'm not going to go into detail about this

You'll also have to swap the drive plate/flex plate from the non-HO engine to the HO engine.(Use the old CPS sensor.) They are different enough to allow it to not run properly. The holes on the flex plate are spaced in a way that it can only be installed one way on the back of the crankshaft. You'll have to remove a plug in the drivers side of the block to install the temp sender and also swap over the knock sensor. Both will be needed with the old wiring harness. In the end the new engine should be configured JUST like the old one.

INSTALLATION:
Lift up the engine and install it according to the service manual. Connect up all the wiring and attach the accessories and vacuum hoses. DO NOT forget the vacuum hoses. These will be slightly different from the non-HO engine and the CCV will also be different. I purchased new hoses from the dealer.

Things you'll need to complete the install:

• New tranny throttle cable (kickdown cable) This will have to be installed by dropping the tranny oil pan and attaching it like the old one. You'll have to get the cable from the dealer..just ask for one for the corresponding year to your donor engine. The throttle body is turned so the cable must now be longer.
• New Accelerator cable. The one that goes from the pedal to the throttle body. This one also needs to be longer because of the above mentioned change.
• New airbox or cone conversion. The CCV layout is now different. You may be able to retrofit your old box. I found someone that had gone to a cone conversion and was no longer using their box. They gave it to me for free.
• New exhaust downpipe. I was able to mate mine using a '92 downpipe but 93+ where different and would not work. You will have to research which pipes will or will not fit. During the engine swap would be a PERFECT time to install an aftermarket header, although I did not because of money constraints. The downpipe may have to be custom bent. Each situation will vary.
• New engine mounts. It's just a good idea to replace them. I'm sure you'll find at least one of them broken and deteriorated.
• New serpentine belt. Might as well replace it now.
• New water pump. Check to see that there is no play in the one on your engine and you might be fine, but for the price I swapped mine to be sure.
• New thermostat - same reason as above.

When all is said and done:
When you're SURE that you've connected all the wiring properly and transmission properly and you've put oil and water in it, hooked up all the vacuum hoses and exhaust, give it a crank and see if she runs. Mine ran REAL rough when I first got it started because I forgot to hook up the MAP sensor vacuum hose. Whoops! Hopefully you were able to get everything running correctly.

Thoughts:
I hope that this article can at least give you some insight into what you're in for in the swap. I had never done an engine swap before but with the help of Dave Kamp and some other folks on the various XJ email lists I was able to get her up and running in about 2 weeks. That was 2 weeks of working 3 or 4 hrs a day and all day on Sat. That's also taking into account all the days I went to work on it then realized I didn't have the right part and had to quit for the day and go home. Hopefully you'll be a little more prepared for the swap thanks to this article.

By - Bob Mock