nhrocker

Yes, it was aluminum terminals. If they were brass they may have lasted longer, but it still would have been just a "band aid" over the real problem. I mentioned earlier in the thread (somewhere in the encyclopedia's worth of text I wrote) that I've soldered the sensor ground circuit splices, cleaned the connections on the block, and added an additional ground to the firewall. The block to firewall and block to battery grounds have also been upgraded. The new TPS tests perfect and the ground on the flat plug now reads 0.0 ohms.

I'm not sure about bulb replacements, but what about just replacing the whole light? I picked up a cheap pair of LED license plate lights for my rig, but I'll be building a whole new bumper that they'll be mounted on. I don't see why you couldn't modify where the stock lights are to mount some of these. Where I ordered mine: http://www.delcity.net/store/LED-License-Plate-Lamp/p_798175

I need to give a HUGE thank you to cruiser54 and his Renix tips! Thanks to him I finally have good news, the hesitation is gone! I spent a lot of time doing research on my problems, and things kept relating back to timing issues. On the suggestion of a friend I had pulled the cap/rotor to inspect them and found burn marks. They had only been in there for about a year. All the internals of the distributor looked corroded and it seemed to have more play than what I would expect, so I ordered a new one. Since the new one came with a new cap/rotor, I cut open my old one to check the indexing of the distributor, per cruiser's write up. Guess what, it was WAY off, about 3/8" off actually. So after cutting the tabs off the new one, properly indexing with a set of feeler gauges, and installing the new cap and rotor, it no longer has the hesitation! It still has a problem with cold starts and a 1500rpm high idle once its up to temp, but I haven't touched the temp sensors yet. I also picked up a new intake/exhaust manifold gasket to try at some point. I haven't been able to find any external vacuum leaks, but I'm wondering if it's leaking between one of the exhaust ports and an intake port.

I run a Dynomax Super Turbo muffler in both my XJ and MJ. I prefer the low, deep tone of them and they don't have the drone that some others are known for. Mine also has no cat, and exits through the frame rail just under the front of the bed on the passengers side and I still don't think it's too loud at all.

Cleaning the IAT is worth a shot. I like free ideas at this point. I've dropped way too much money into fixing this with no real results yet. :???: The stop screw itself has not been played with. It is not a renix TB just for reference. It's a HO off of a friends stock '99. I bored it out to 60mm myself. I did not mess with where the butterfly "seats" so to speak. Only took off the restricted section. It's sitting on a .538" thick aluminum adapter I also machined to 60mm to match the TB. The coolant temp sensor was one of my earliest questions. The one on the top/rear of the head for the gauges was replaced when I first got the truck and swapped in a full gauge cluster. The one on the side of the block looks original and no parts store in town even lists/shows a replacement for some reason. I believe I've found the correct one through Rock Auto (the one with the two wires coming out to a plug). It's around $17, so not too bad for me to try. Truck is about to hit 180k miles, so it would need to be replaced at some point anyway. Can you tell I'm used to trying to justify why I'm willing to do what I do to my Jeeps? :cheers:

So the hesitation got even worse. It was doing it as low as 1800rpms, and when it got really bad started bucking as well. I found that the fuel pressure regulator was junk when someone suggested I check it. I pulled the vacuum line off and gas started coming out. I just replaced it with a brand new one. The hesitation is still there, but is much less noticeable and it no longer "bucks" at all. It still only under decel or holding speed, issue goes away under full throttle. The low idle on a cold start is still there. The colder it is, the worse it is. A few days this week it wouldn't stay running it was so low without giving it a little throttle. Once its up to temp its back to idling at 1500rpms again.

Well, with the truck back on the road finally I had a chance to try some things. I've found that the hesitation will occur in any gear once its at or above 2,100rpms. Still only if its either holding speed or decelerating. If I'm into the gas at all it seems to go away till I let off. It also doesn't like cold starts. It never had this problem before. If its cold at all I have to leave the hand throttle up a little to keep it idling or RPMs drop too much and it stalls out. Once its up to full operating temp it still idles between 1000 to 1400rpms.

TPS is now brand new, and set properly. Ground at plug shows 0.0ohms. It made no difference in the hesitation or idle issues. I did find excess oil in the TB and intake. I'm running a HO valve cover and grommets/hoses which are all clear, no plugged ports. The oil appears to be mainly coming out of the front hose off the valve cover which connects back to a barb fitting on the adapter I made to run a conical filter. Since my last post I also had both the ignition switch and cylinder die. While sitting to replace those I found the fuel tank was leaking. It now has new ignition cylinder/switch, new gas tank/straps/pump/screen/filter/soft lines, and new spark plugs. The color on plugs 1 and 5 were a little darker, and when I checked they had just over a .040 gap. I know they were .035 when installed. New plugs set to .035 and the hesitation is still there, but didn't feel as bad to me (it may be just me hoping for any improvement at this point...).

My XJ has a TnT track bar setup in it (uses the same RE joint for the frame connection), and I could never keep that bolt tight. Once it loosened it would wear out or just start stretching. I got used to checking mine all the time and always carried a spare bolt. I think I changed it about once every year or two while I was still driving it. It's been parked for a while now, but if I ever get back to working on it I'm going to try boring the center ball of the joint out to take a larger bolt. It just seems too small for the potential stress it sees.

As mentioned in the first post, I've already opened and checked the harness grounds. I soldered the connections, and while there soldered in an additional ground that's connected to the firewall. Both the block to battery and block to firewall grounds have been upgraded to much larger cable with solid end lugs. Originally the grounds at the TPS and IAC were reading around 1.8ohms. I got them down to a very minimal number (can't remember what at the moment). It's a '90, so no c101 to worry about. Sounds like I'm on the right track thinking the TPS is on its way out. I tried testing it in the past and couldn't get a good reading. I was thinking I might have been doing something wrong, but maybe it really is just faulty. You mention the auto TPS being usable, which is much better priced and available. I may just pick up one of those and try tuning that in instead of messing with mine anymore. And no input on the temp sensors? Seeing that all my running/idling issues are temperature sensitive I'm pretty sure one if not both of them are faulty, but don't know why I can't find them available anywhere.

The starting issue isn't the fast idle. It will briefly rev up to over 2,000rpms, but then drop back down to a normal idle. Other times it will start sluggishly and idle at around 200rpms. About 75% of the time it starts and idles fine. The fast idle only occurs after its been running for a little while and comes up to full temp. I originally thought IAC as well. When I pulled it to clean it it came out in pieces. I replaced it with a brand new one and it still does it. I believe the combination of new IAC and re-grounding the harness is what brought the idle at temp from 1500-1700 down to its current 1200rpms. Better, but still not where I'd like to be. The injectors I used were purchased from Precision Auto Injectors. They are the upgraded 4 hole style that are rated for Renix or OBD1 HO motors (running stock 39psi at the fuel rail) already. I had called and spoken with him on the phone and listed all the modifications to my MJ and he was confident that larger injectors weren't needed unless I was going stroker or forced induction. I don't think I'm reaching duty cycle on them, because its only under partial or no throttle that I have the hesitation. If I'm into the throttle more, either to accelerate or if I'm trying to hold speed up an incline, the issue completely goes away. I would think if I was at duty cycle already at partial throttle, wouldn't there be nothing more to give if I stepped on it? My thought process was if its throttle related TPS and o2 would be the largest culprits. Both appeared to be original. I used to get the hesitation as low as 35-40mph. When I unplugged the o2 and drove it for a couple weeks, it got rid of the hesitation below 50mph. I installed a new o2 sensor and the hesitation below 50 hasn't come back. So I was thinking the remaining hesitation over 50-55mph should be TPS related? I was thinking if the $20 2.5L TPS from Rock Auto will work for my 4.0, I would pick it up. And with the high idle related to the engine temperature, either the coolant or manifold temp sender must be faulty. But those I can't even seem to find available at all.

Trac locs are great. I'll bet if you toss one in you'll be very happy with it. Great for DD and most wheeling duties if you're not looking at big tires or low gearing. For me they weren't going to cut it. I'm a fan of low gearing. I was also going to 4.88's and used my XJ for rock crawling. Guys I knew with Trac Locs said they weren't nearly aggressive enough. The True Trac was actually pretty aggressive for a LS. If I stayed into the gas in a tight turn the rear would stay "fully locked" and I could lift a tire clean off the ground. Scared a few friends watching me do it more than once. I wasn't gentle on my rig at all, so durability was a big thing for me. With the 4.88s and 31's I was snapping stock front shafts and u-joints. Upgraded to alloys and 33's, then cracked an alloy shaft. Upgraded again and then went to 35's and then decided to sell the axles. Found out after pulling them I had blown teeth off my ring gear with the 35's. During all that, the rear end with the True Trac still looked as good as the day the gears were set.

I recently switched to Lube Lockers in my MJ. I do all my own work and maintenance and had finally gotten sick of cleaning RTV off. I plan on keeping my MJ for a long time, so I know I'll be doing maintenance on them again. If you think about the cost of the RTV, gaskets if you use them, and whatever you use to clean the old stuff off, it only takes a few times doing it to add up to the cost of the Lube Lockers. Plus with the Lube Lockers, draining and refilling is easy. Loosen cover, drain, tighten back up. No waiting for RTV to dry, no need to add a drain plug, don't even need to fully pull the cover or clean the surfaces again. For gear oil, I've been using Lucas in both my rigs for years. After talking with 3 different guys that set gears professionally, it was the only gear oil they all recommended that was readily available locally. It was even the same price as the "cheap stuff." Its also formulated so there's no additives needed if you have a clutch driven limited slip.

I know you're looking for something more inexpensive, so I hope you don't mind me giving my experience. Years ago when I was deciding what I wanted to do in my XJ for lockers, I was convinced to try out a Detroit True Trac in the 44 I was swapping in. For about 5 years it was my year round DD and wheeling rig here in New England. First on 31's when I put in the lockers, then on 33's, and then on 35's. The True Trac never let me down. Being gear driven I didn't have to worry about additives, no clutch packs to worry about, and there were no bangs, pops, ratcheting, etc like with auto lockers. Nothing against auto lockers, I've driven rigs with them as well, but I much preferred the True Trac for both on road and off. It was still plenty aggressive for wheeling, but not so aggressive like full lockers can be that I was worried about breaking shafts or ring gears, even on the 35's.

Since I've owned my MJ I've been battling pesky little problems. Many of which I've figured out over time. Between the repairs, upgrades, and modifications I've done it's like a whole new truck, but it still has issues. For reference it's a 1990 MJ, 4.0 Renix, 5speed, NP231. I'll start with the remaining issues. Upon startup the majority of the time it starts fine. Once in a while it will either rev high (as high as 2000rpms) then drop down to normal, or start extremely low and take a while to speed up to normal idle. Out of starting it multiple times a day, every day, it will do one of those two conditions maybe a couple times a week. The next issue is a high idle, but not consistent. When cold it does not idle high, but as it warms up, the idle increases. It used to idle at around 1500rpms consistently, but with work I've gotten it down to around 1200rpms. It doesn't always do this, some days it will idle at 1000rpms or less. Those issues alone don't worry me too much, since during normal driving they don't seem to affect it at all. The biggest concern is a hesitation it gets at 50-55mph and above, when either holding speed or decelerating. It feels like a hesitation, stumble, mis, or something like that, which you can feel. The whole truck feels like it pulls back each time it does it, but it doesn't make any extra noises or anything. I've found if I'm going down a hill at any speed and leave it in gear to help hold speed down or decelerate it does a similar hesitation. It only seems to do this when up to temp. Now onto what I've done so far. In working on the truck to repair and upgrade it I've replaced or modified a lot. Almost everything I've done has improved something about the way it drives or its performance. For the intake, I made an adapter to run a conical oiled filter. It hooks into a HO throttle body I bored to 60mm straight through. The TB is bolted to an aluminum adapter/spacer to allow it to bolt on to the Renix intake manifold. I also made an adapter to allow the stock TPS to be bolted back on to the HO TB. Along with that I installed a later model HO valve cover with an upgraded gasket. The EGR system has been removed and a blockoff plate was used on the side of the intake manifold. All vacuum lines relating to the egr, transfer case, and front axle have also been eliminated. What vacuum lines remained in the engine compartment have been either replaced or checked for leaks. So far I have not found any leaks (there could be some from movement/vibrations during driving). The valve system for the heater lines has also been eliminated. I still do not have heat, but believe it to be from a clogged heater core. The catalytic converter has been removed, and a Dynomax Super Turbo muffler was installed with an elbow off the back of the muffler going throught the frame rail exiting just under the front of the bed. It has recieved flow-matched 4 orifice fuel injectors, new IAC valve (old one came out in pieces), and new O2 sensor. While checking and resoldering the ground connections in the harness, I also added an extra ground direct to the firewall, as well as cleaned the grounds to the dipstick mount bolt on the block. I've replaced the oil pump with a high flow unit while in there doing a new rear main seal, as well as an upgraded oil pan seal. While in there I did find some large deposits in the bottom of the pan, no metal though. Roughly 3 to 4 tablespoons of deposits. I found no water in the oil, and have never found oil in the coolant. When I first purchased the truck it never got up to operating temp. I found that someone had installed a 160 degree thermostat. I imediately replaced that with a 195*. I also converted it to an open system using an inline filler neck in a new upper radiator hose. After issues with that blowing hoses off I replaced the water pump, and put in another new 195* thermostat. It has been fine since and temps respond as they should, checking both the guage inside and verifying with an IR thermometer. I have also been paying attention to the mechanical end of it. Both axles were replaced with a set of D30/Chry 8.25 out of a 99XJ with 4.10 gears. Both were fully cleaned/rebuilt as needed before install and within the past 2 months have been reopened and checked. They're in great condition. All u-joints have been replaced within the last 2 years or less. Transfer case was replaced a couple months ago as well. The only things that leaves I feel could have any affect on these issues is the transmission (I did drain and upgrade the fluid while swapping the t-case, fluid looked fine), clutch, or internal mechanical issues with the motor. So I'm narrowing this down. Things have been improving. Like mentioned, it used to idle at 1500-1700rpms, and it also used to get the hesitation as low as 35mph. Somehow through all this work it is getting better. The fact that the issues are not conistent has me hoping its still just an electrical/sensor issue and not something mechanical. I've pretty much decided to replace the TPS, since adjusting it doesn't seem to make a difference at all. I'm also thinking the MAT sensor and/or coolant temp sensor need replacing since many of the issues still seem to be temperature related. Thats where the confusion comes in. I can't seem to find MAT sensors available anywhere. Am I looking for the wrong term? Parts stores and Rock Auto don't show them at all. For the coolant temp sensor, everything I find seems to be the sender for the guages, not the one in the block. Again, looking in parts stores and Rock Auto has me coming up empty. Then theres the TPS. When searching Rock Auto they show one under the 2.5 engine that looks identical to mine, and for less than $20. For the one that looks correct under the 4.0 its $106.79! Will the one for the 2.5 work on my 4.0? Sorry for writing a book on this guys. Just hoping with as much info as possible someone out there can help me with this. I love my truck but am getting really frustrated with these issues.

I used a '96 junkyard booster to upgrade my '90. I did use the spacer, so I didn't have to bend the lip. The washer bottle was relocated further forward. I made the stock pedal and brake switch work by cutting the end off my old and new rods (after carefully measuring to get the length right) and welding the end of the stock rod onto the '96 setup. Pedal is the proper height and brake switch works better than before after cleaning it while it was out.

First thing I would check is the group of grounds on the side of the block where the dipstick tube is bolted on. Remove the bolt, clean well, and reinstall. My own MJ did similar to what you describe, I started throwing parts at it, just to find out all it needed was the grounds cleaned up, which was free and only took a couple minutes to try. If that doesn't make a difference in starting, next I would check the lead from your battery to the starter. They are notorious for failing in MJs/XJs. Even if the ends look fine, the wire inside the insulation can become dry, brittle, or corroded and fail. You can try wiggling the ends of the wire while someone tries starting it, or easiest way I've found is to use one lead of a set of jumper cables. Clip one end directly to the battery and then the other end down to the nut where the end of the wire connects to the starter. If it starts then you just need a new power lead and/or battery terminal. Other easy to check items that could cause issues like this are the main grounds to the battery. Make sure both ends of all the grounds are clean and in good shape, especially the one going directly to the block, as it's the one that would most likely affect your issues.

I'm guessing you're looking for the stock bushing width, or direct replacement size? That would be roughly 2.625" wide with a 9/16" bolt hole.

I've been running Dynomax Super Turbo mufflers on my XJ for years. Always love the sound of them, so I picked up another and tossed it on my MJ. At the time I got it for around $40 shipped, now I think they're up to like $52 shipped? Still not bad IMO. Cat delete, no tailpipe, tip goes through the frame rail and dumps out the side near the front of the bed. I love the way it sounds. Nice deep tone, no high pitched noises whatsoever. It's got to be one of the lowest tones on a 4.0 I've ever heard. It's actually deeper sounding on my Renix MJ than on the HO XJ.

I love my XJ and all, but man has the bed on my MJ made life so much simpler... Carried 4 stock XJ rims/tires plus a set of 5 33x12.5's on rims a couple weeks ago. I never would have fit them in the XJ. Now if only some of them were MY rims and tires and not just picking them up for friends... :doh:

About the Ected, I'll second what CW said. I'm currently on my 2nd Ected in my D30 on my XJ. First one wouldn't ever lock up. This one now works when it feels like it. A friend has gone through 3 in his 8.8, and he thinks he finally got one that works correctly. Another friend went through 2 in a D35 before he swapped to an 8.8, and is in the process of trying to swap the coil from the last one (now blown) into his D30 Ected that the coil died in... In theory it's a nice design, but it's rare to ever see one work properly.

Thanks for bumping, that'll come in REAL handy! :thumbsup:

Sounds like you just need a bigger hammer! :cheers: Haven't had to do floors in an MJ yet, but I've done four XJ's so far. For most parts I used either 14 or 16, depending on what I could get for free/cheap scrap from my supplier. In XJ's the areas around both ends of the spring hangers are the first to rot out, and those I typically redo with 1/8" plate to make sure they don't go anywhere again. All pieces I form by hand to fit. Hopefully you fully ground off the galvanized surface before welding? Welding with the zinc coating still on there can release some nasty stuff that's very hazardous to your health.

I'm up here in New Hampshire. Been around the XJ world for a while now, so I know some names in here from NAXJA and other sites. Recently picked up my MJ thanks to this very site! It's already been put to use as a DD and has gotten a few repairs and upgrades, with plenty more planned. I'm working hard to resist the urge to go bigger with it already. I just keep telling myself it's my DD, the XJ is my wheeling rig...

On my MJ, not even sure. Mismatched set of 225 or 235 all seasons... They work and pass inspection so I wasn't too worried about looking at them more yet. On my XJ I've had great experience with Goodyear MT/R's. I've run 245/75 R16 MT/R's, 33x12.5 R15 MT/R's, and the newest set is 35x12.5 R15 MT/R's with Kevlar (the new style MT/R's). I love 'em. They get me through anything I throw at them, including getting me to work since my XJ is/was my DD. I live in New Hampshire so they've seen some nasty weather and I've always felt confident in their performance. So far on the new MT/R's I've been even more impressed than the old ones. They are actually quieter on road than my 33's were, yet they have more aggressive outer lug spacing. I've used them on road and for some snow wheeling so far, but come this spring/summer I'll be starting to test them out on the rocks. I expect them to do well, but time will tell.