Nathan9Mile

Is it really worth it? If you have a good running renix why rip it all apart for the very little gains you will get? This is just my opinion. That is alot of work for at the best a 13hp gain and 1ft pound of torque. Everything I have been able to find rates 87-90 renix engines 177hp at 4500rpm 224fts at 2500rpm. 91-95 190hp at 4750rpm and 225tq at 4000rpm. Also the 96 engines same numbers but changes in cams lowerd peak torque to 3000rpm. As u no ho engines got the bigger injectors bigger throttle body better flowing intake and exhaust manifolds along with different cam timing over the renix. As far as I no you cant really change the cam timing running a renix computer. So your missing out on 2 things the better engine management and the cam timing who is to say you will even see the 13hp and 1ft gain. The biggest problems with a renix is renix lol. If your keeping it renix powerd (I would) leave it alone and run the **** out of it. We rely on torque wheeling not so much relying on hp we are not drag racing. Just seems like alot of hassle and money for the very small gains just my 2cents buck

outlawcherokee

I did the HO swap on mine. All started with buying the wrong header for mine and ended swapping the top end from an HO and went with the upgraded injectors as well. Used the renix tps on the HO throttle body with a very simple mod. What seems like a very small amount of increase in power it made a huge difference. My commute at the time had me going up a large hill on the freeway that pre swap I had to drop to third gear and lose my speed, post swap I could leave it in 4th just take off lockup and still maintain freeway speeds. Overall it was an easy swap and well worth the money spent at the local pick n pull.

SHANE 87

Hello Buck, I am liking the army life so far. I am only in the reserves to start off, since i only have a GED they wouldn't let me start as active. I will be back in Washington after I finish my training. I don't have an exact date on when I finish my training because I am recovering from a hip injury. to the best of my knowledge I should be done in 3-4 months

BuckB91XJ

Thanks for all of your inputs, guys. This is the kind of talk I like to spike here on the forum. Nathan and Outlaw both have good points backed by good facts. I do have a good running RENIX motor "as far as I know". The PO really wasn't much help in trying to figure exactly how many miles are on this motor that is in this Jeep. The Jeep has 230,000 miles on the odometer. However, the entire long block is painted a bright like "Chevrolet" Orange. The Jeep 4.0 was never painted orange by the OEM none of the years it was used in the XJ that I am aware of. I'm figuring either the original motor was pulled out and rebuilt, or another engine was acquired, painted and prettied up and then installed into this Jeep. I really think the original motor was rebuilt or replaced based in "seat of the pants" feel while I was driving it. The motor in this jeep has LOTS of power, it doesn't blow a bit of blue smoke when started up cold, when started up warm, when run in stop and go traffic or when run at high speed on the freeway. It does have a miss at idle that I think is being caused by the straight pipe exhaust that is on it. However it also does a weird "hunting" thing that it does between 3rd and 4th gear when you try to make it kick down from 4th to 3rd at around 50-60 mph. I was thinking that may be caused by a bad or mis-adjusted TPS. I really need to do a compression test on the this motor so I really know for myself what the health of this motor is.

BuckB91XJ

On the other side of the coin. It really would not cost me much at all to do a complete HO top end (e.g., head, exhaust manifold, intake manifold, injectors, fuel rail, throttle body) as I already have perfectly good pieces sitting in my garage....and a complete cold air intake with spectre cone filter and 2.5" exhaust with flow master super 40 muffler. I think the combination of all of these parts will really wake this motor up and make it breathe MUCH better. If I make a 20 hp gain that is huge!

Nathan9Mile

I understand why you wanna do it buck and if you have all the stuff go for it I was just throwing the info out there. Since you are using that used head I would at the very least check it out to see if it is warped. You would be very surprised how even a non over heated cylinder head can be slightly warped. Might be money well spent to get it checked out

BuckB91XJ

Thanks for all of your inputs and advice. And you do make a good point. I totally agree that id something isn't broken a guy shouldn't try to fix it. Keep you inputs coming I enjoy reading them.

Nathan9Mile

Thats what we are all here for I love hearing what people think too! Im a big fan of the not broke dont fix it mentality but I guess if we all did that we wouldnt be into modding our xjs lol

BuckB91XJ

I pretty much got my exhaust from the old jeep put on my new red jeep. the installation didn't go and smoothly as I expected but, does anything you do on an XJ ever work out that way? It was dark when I came in and it still isn't finished. The old straight pipe came off easy enough. Come to find it was only clamped on. All of the pipe hangers lined up perfectly. I broke the stud on the tailpipe hanger so that and the fact that my old tailpipe isn't fitting very well with the stock flat leaf springs, has considering cutting the tailpipe of after the muffler. Then, I will have a new exhaust system put on my red Jeep after I get the lift and axles put on it. I had already installed the 4.5" lift lit on my gray Jeep before I had this exhaust put on it. That's why the side exit behind the right rear tire tailpipe isn't fitting right. I will take a couple pictures tomorrow after I finish up so you guys can see what I came up with. I think this exhaust will be a huge improvement over the straight pipe that was on it.

outlawcherokee

no no no you got it all wrong... If it isn't broken fix it till it is

sometimes I look back at pictures of when I bought mine and think wtf did I do. It was clean, straight, mild lift and exactly what I was looking for 2dr manual. Now the only thing that remains of that jeep is the short block and body .

BuckB91XJ

Oh don't get me wrong. I like and appreciate Nathan's input. I'm looking forward to seeing that monster XJ he is building and going wheeling with him someday. BUT....I have driven an XJ with a 4.0 HO for years and I have now driven an XJ with a 4.0 RENIX. It became obvious to me when I installed my Do It Yourself Cold Air Intake that I built for my 91 4.0 HO motor, on the 87 RENIX motor in my new Jeep. It was literally a night and day difference in acceleration just by doing that. It made a WAY bigger difference in "seat of the pants" feel than it did when I installed on my HO motor in my 91 Jeep. I believe this is because the stock components were geared more toward reducing noise levels and and emissions, than providing optimum performance. I will be swapping the OEM top end on my RENIX for the HO pieces I have in my garage. I am going to look that head over really good that I took off of that blown 96 HO motor, before it goes on my Jeep. It really surprised me when I removed that head and saw that number 5 piston completely demolished and yet the head combustion chamber, valves and and even push rods were fine and unbent. After doing the CAI I was looking forward to seeing if that would wake it up even more.

BuckB91XJ

Well, I actually got quite a bit accomplished on Ole Red today before the Saints/Eagles game started. Here is what the exhaust looked like when I finally got it in and all clamped together. Installing the muffler actually quieted it down enough that I was able to hear that it had an exhaust leak up by the motor. I took a look and listen and realized the pipe that runs between the exhaust manifold and the intake manifold for the EGR was not connected to the intake. The fitting was completely loose and the pipe was just loosely in the hole. I tightened that up properly and the Jeep idle smoothed a bit and the exhaust note sounds just as good as it did in my old Jeep. Love That Flowmaster!!! I then took some Carb. cleaner and a tooth brush and cleaned out the throttle body and the IAC. Sense I re-installed the IAC the Jeep is idling a little fast. I'm not sure what is up with that. RENIX gremlins or Karma for messing with something that wasn't broke...LOL. I was going to test and if need be adjust the TPS but, I found my DMM had a dead battery. By the time I rounded up a new battery and was ready to do it I'd run out of daylight and it was time to watch the game. Tomorrow is another day. Oh speaking of the RENIX gremlins...Since I bought my jeep the inside left turn signal light and the heater control back light had not worked. I just took my jeep for a test drive after doing all the stuff I'd done to it today and the the left signal light and heater back light mysteriously started working. I'd even bought new bulbs for them to swap out when I had time. I'm sure those lights will continue to come and go until I figure out what is causing the problem. Gotta love the challenge of RENIX Electrical Gremlins...LOL.

BuckB91XJ

I have been doing a lot of reading over the past couple days. It appears inferior electrical wiring, wiring components and practices used in 1987, the first year the 4.0 motor was installed in the Jeep Cherokee, has caused a lot of issues. Unfortunately these issues are the kinds that cause logical thinking people to replace expensive sensors.
Based on what I have found out doing some basic electrical cleaning and upgrading before I address any high idles or hard starting.

1.) I will be cleaning up the dipstick area block grounding stud and the even half dozen wires connections that are connected to it.
2.) I will be cleaning up the connections on the grounding strap that goes from the left rear head bolt to the a bolt on the firewall.
3.) I will be adding a 4 gauge ground wire between the firewall bolt in number 2 above and either the most rear heat shield bolt on the intake manifold, or the most rear fuel rail bolt on the intake manifold.
4.) I will be adding a 4 gauge ground wire between the (-) battery cable clamp and the nearest radiator support 10mm bolt.
5.) I test and if required fix the Sensor Grounds.
6.) I will be adding a 10 gauge ground wire between the OEM Instrument Panel ground bolt and the 8mm stud above the driver's kick panel.

I will also be doing a good cleaning of the infamous C101 connector on the left side firewall. Once all of that has been addressed only then will I entertain any electrical or "RENIX" issues.

OleBlue

Someones been reading Cruisers posts!!! Lol, hes the man when it comes to renix! Have learned alot from that dude.

BuckB91XJ

Hey, Buddy. As you know I am new to the world of these Antique XJ's we all affectionately call "The RENIX XJs". I've been an all HO guy for the 8 years I've been in the XJ world...other than what I have learned from helping my son Chris work on his 87 XJ, all my experience has been with my 91 Sport and 96 Country. My "new to me" 87 Laredo is opening up a whole new world....and I am thoroughly enjoying the challenge. I love this Jeep. It's about the cleanest 87 Cherokee I think I have ever seen.