90 XJ Engine swap HELP

Well its been almost 5 year since I have been on here and since I sold the ol D60/40'S 88 XJ rock crawler for my truck and ended up picking another 90 xj, great jeep for about a year until the odom read 220k and then she let me have it. I literally have replaced almost every driveline component minus the block and internals. I had the top end rebuilt about 20 k ago and started having over heating problems. Replaced the closed system with an open and the heat issue went gone along with an alternator, h20 pump, rear main, pan gasket, both shafts and joints, head gasket, valve cover gasket and all the dang vacuum fittings left. Not to mention a ton of other crap in the axles and the list goes on. Recently the valve cover has had a ton of pressure created in the case and I'm clueless to know where the pressure is coming from. Had the cooling system checked for hydro carbons, compression tested and all were ok except for #6 which seemed a little low. Vacuum is stonng and with the oil cap of I can see a continual puff of vapor at idle(like one piston is blowing), and the amount of air flow around 3k is insane. Put it this way I can blow a half a court of oil out in 100 miles.... I have a 1 gallon catch rigged up at the moment to get me by.


Any ways to get to the bottom of it I am blowing a ton of oily vapor out of the valve cover, figure I need rings and do not have time for a motor rebuild in between my races during this season. its a 90 xj with an inline six and I was wondering what year of L6 will work example 90-2000 or 2001 and up. I have heard there were difference and I just want a bolt in setup/swap. I'd like to find an HO since I tow a ton with it and the 33's are already killing me enough. I actually was looking into a stoker but figured its not worth it at the moment for me. She did fine with an intake, straight pipes, header, and a spacer before...enuff to tow a couple bikes and tools.

So fellas what year L6 will work? ebay and and the local yards have a ton of them around for close to 500.... with low miles .... or any opinions on what it may be? I have so much air flow out I can only see it being rings.... never seen this much out of a jeep.

Thanks guys... oh yeah how can I post pics?

:twak::flame:

87-90 engines would be exactly the same. The HO versions use different computer systems, and either need to be adapted to the old, or the entire wire harness needs to be swapped to make the new computers work. I assume the same can be done with the newer "Power Tech" engines, although I've never heard of any of the 00-01 (?) models with the coil packs being converted to the old Renix system, so I don't know if it can be done. probably.
There's different ways of getting er done, I have a 93 4.0 in my 87, and I did it not the easiest way, but not the hardest. More problems could be run into if you need to pass emissions tests (visual inspection), as the Renix system uses an EGR thingie which is usually ditched for several good reasons in a Renix conversion. It could be kept, if you go the "easiest" way, but performance would be better if you go the way I did(use HO intake manifold), or the "stupidly hard" way(swapping computers). let us know what you want to do, and I can probably help, or i could do it for you for $900 or so

Appreciate the info, I'd rather just go with swapping the intake manifold than the entire computer, and luckily I do not live in an emissions state, however I notice you are out in IL, I'm in CO, so how would that work haha. I have done quite a few old chevy swaps that were easy but am new to what is interchangable with the 4.0. There are a lot of local 4.0 available, but I have always rebuilt my motors and am actually really hesitant in trying to find one that I can swap with my current one. They all have a ton more miles than mine currently does, and I do not want to run into this problem till I sell the thing in about 3 years. Anyone have any links to a good salvage yard that is willing to ship. I'm not trying to go past 600 bucks for a decent motor.... more if it a reman but not more than 1k,


What is the difference?

6-242 (4.0L, VIN "L"), AT
6-242 (4.0L, VIN "L"), MT

Have you serviced your CCV system?

car-part.com is usually good for finding local salvage yards.

To convert to Renix, you will need every single sensor to be swapped over to the new engine. You'll also need to use the old alternator. You'll want to use the old PS pump, or at least the hoses, in order to connect to your steering box. The easy/hard part is where it comes to the intake manifold, since you need the old TPS in order for it to run, and the old fuel injectors in order for it to not get 12 mpg. The easy way is just to run the entire old manifold, fuel rail, injectors, and TB. The hard way involves adapting the TPS to the HO TB, and swapping injectors. I used the (better) HO intake and (larger) TB, I adapted the TPS, and I still have not swapped the injectors, so I get about 12 mpg. (Probably doing injectors today) There is an adaptor available from Hesco, to adapt the TPS, but I just kinda rigged it. Let's see, if you swap the transmission as well, you need to use the old flywheel or flexplate, as the Renix CPS will not read the HO flexplate or flywheel. It won't even start with the wrong one in, this actually made me pull the entire engine/trans/TC twice because I didn't swap it at first. I think I kept the HO t-stat housing in order to fit one of the Renix sensors in, but I'm not sure which it was.

Good luck with all this, I think I'm gonna go swap injectors

ccv as in the valve in the back with the gromet correct? I replaced the breather valve and the gromet when I cleaned the valve cover and replace the breather hose up front with a gromet and PCV since it was no longer venting into the cover but rather becoming another vent out. Had the the PCV vent out into a quart bottle till it started to get pretty bad thhen I knew something was really wrong. I looked up a lot of this stuff on the net as well and tried to remedy it with info others had.

Put it this way when I popped my air box cover the entire filter was soaked, intake hose soaked, leaking out of the air box drain hole... literally a quart if not more was just in this area.

Currently once the motor is warm its like heroshima coming out of the valve cover vents... I have never seen this kinda flow on a motor before, thought I had a stuck valve or something after I heard a valve knock start soon after it got bad, all in all I really don't know what else it can be besides a ring problem, which is just a little foolinng after the compression test. I am an engineer myself and do NOT understand some of the logic behind the vacuum system on the cherokee. And have not fiddled with it much on my old cherokee that never had this problem even through the abuse I put it through. This one has been babies compared to my 88.

Found a few yards to get a motor but I am still having a hard time considering buying a motor with only 60k less than mine, I guess as long as it gets me by for three years I'm ok with it.

here ya go
http://www.terrainstompers.com/forum/viewtopic.php?t=14

Slip Kid said:

To convert to Renix, you will need every single sensor to be swapped over to the new engine. You'll also need to use the old alternator. You'll want to use the old PS pump, or at least the hoses, in order to connect to your steering box. The easy/hard part is where it comes to the intake manifold, since you need the old TPS in order for it to run, and the old fuel injectors in order for it to not get 12 mpg. The easy way is just to run the entire old manifold, fuel rail, injectors, and TB. The hard way involves adapting the TPS to the HO TB, and swapping injectors. I used the (better) HO intake and (larger) TB, I adapted the TPS, and I still have not swapped the injectors, so I get about 12 mpg. (Probably doing injectors today) There is an adaptor available from Hesco, to adapt the TPS, but I just kinda rigged it. Let's see, if you swap the transmission as well, you need to use the old flywheel or flexplate, as the Renix CPS will not read the HO flexplate or flywheel. It won't even start with the wrong one in, this actually made me pull the entire engine/trans/TC twice because I didn't swap it at first. I think I kept the HO t-stat housing in order to fit one of the Renix sensors in, but I'm not sure which it was.

Good luck with all this, I think I'm gonna go swap injectors

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all right I'm going to just try to find an original motor then, I do not have time for all that. BTW what does RENIX stand for?

jfiscus said:

here ya go
http://www.terrainstompers.com/forum/viewtopic.php?t=14

Click to expand...

Thanks for the find....

Nik said:

Found a few yards to get a motor but I am still having a hard time considering buying a motor with only 60k less than mine, I guess as long as it gets me by for three years I'm ok with it.

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Lol, I swapped in a motor with 200,000 miles on it, which was only about 10k less than mine. Tho, it was free, and I did not have much of a choice The "new" one's at about 225k now, the old one popped at 211k, my Jeep itself has 236k, or, about the distance to the surface of the moon.

Nik said:

all right I'm going to just try to find an original motor then, I do not have time for all that. BTW what does RENIX stand for?

Click to expand...

Renault/Bendix

Nik said:

Thanks for the find....

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That was me a few years back, they make a HO-Renix adapter; should be somewhere linked on that page, but I just made the DIY version, still may have it sitting around if a picture would help. Jeep ran fine that way for over a year, then I got a GOOD body & took hat motor back out & put it in the new body, still running fine another year + later.

Slip Kid said:

Lol, I swapped in a motor with 200,000 miles on it, which was only about 10k less than mine. Tho, it was free, and I did not have much of a choice The "new" one's at about 225k now, the old one popped at 211k, my Jeep itself has 236k, or, about the distance to the surface of the moon.

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:cheers: Well I am just going to stick with a direct swap motor, all of the vacuum and sensor jazz is making me pretty sure I'll fugg it up somewhere. Wish this did not happen during a time of pulling strings to make money.

Slip Kid said:

Renault/Bendix

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:wave:

Nik said:

:cheers: Well I am just going to stick with a direct swap motor, all of the vacuum and sensor jazz is making me pretty sure I'll fugg it up somewhere. Wish this did not happen during a time of pulling strings to make money.
:wave:

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Understandable, but if it is any consolation, this was my first motor swap ever & everything went smoothly, but I did have both entire Jeeps sitting there for parts. Good luck on whichever your decision is. I know the new HO motor definitely had more pep than the Renix 4L did, but 150k is a big difference.

well If I went that route all I would have is the motor. and my jeep that it would go into, .... one other quick question, when you knew yours was done, was it blowby or a catastrophic failure?

Nik said:

well If I went that route all I would have is the motor. and my jeep that it would go into, .... one other quick question, when you knew yours was done, was it blowby or a catastrophic failure?

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Mine was I suppose catastrophic failure, as I was on the interstate, tried to go 80, and was welcomed with plumes of exhaust smoke, and knocking, then it died. I've always seen blowby as something that just happens with these engines.

Nik said:

well If I went that route all I would have is the motor. and my jeep that it would go into, .... one other quick question, when you knew yours was done, was it blowby or a catastrophic failure?

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Mine had the headgasket going bad & I was offered the other complete (wrecked) XJ for $225. Seemed like a logical choice.

Man you guys are getting some steals on Jeeps, I'm still looking at motors with 100k+ miles for 600 bucks locally, still have not found one that sounds worth it yet.