jeepcoma

4.0 HO, 5-spd, 4x4. It's a LWB though. http://comancheclub.com/topic/51990-fs-in-nh-91-comanche-lwb-4x4-5-spd-2500/

Hi everyone, I've recently noticed a new problem on my '91 4.0. When I first start the truck, it idles perfect at the normal RPM (~750 on the tach, or whatever the first line below 1,000 indicates). I can rev it, I can drive it, it's smooth and returns to the correct idle every time. Not long after, with no apparent change in the way the engine runs, it'll idle really really low (to the point of just stalling out on occasion) when I put the clutch in to come to a stop. If I veeeeerrrry gradually bring the RPMs down, either in neutral and using the gas pedal, or say being in 5th gear and slowly decelerating until the RPMs are about 750, it'll hold the correct RPM. It just needs some encouragement. More abrupt RPM changes, like from normal driving and clutching, result in the low RPM/stall condition. If it DOES stall, and I pop the clutch to restart the engine, it goes back to normal (correct) operation for a while again until it starts all over. I've done some research on this and the conventional wisdom is a problem with the IAC. I do not believe this is the case here because it doesn't always exhibit this behavior, and it briefly goes away after a stall/restart. It's independent of both ambient air temp and coolant temp. Since it takes a few minutes of running for it to occur, I'm thinking it's a computer issue with open loop vs closed loop operation. I haven't put it to a stopwatch or anything but I bet it takes the same amount of time for the problem to start. Anyone else run into this or have some ideas? It never fails that if a problem is going to start, it'll be the dead of winter, when it's both freezing cold AND I have to bring the truck in for inspection! :wall: Maybe I can say I installed one of those new-fangled start/stop systems to save gas...

I did a writeup of my experience, complete with part numbers and pictures. You might find it useful! http://comancheclub.com/topic/30325-complete-brake-overhaul/

Long-term update to this thread. I recently purchased the Novak cable shifter adapter kit SK2XC to replace my broken stock linkage. I thought it would be an easy plug and play deal, but the Jeep gods frown upon such talk so I was cursed with trouble. Naturally, I had to cut the original linkage system off the body. This resulted in nicking the plastic clutch line with the cutting wheel (on the last bolt, no less). OK, fine, I wanted to upgrade to the stainless kit from Advance anyway as mentioned in this thread. Naturally, they are closed for the holidays, so I was forced to find a fix so my wife can get to work. I managed to rig a temporary repair by flaring both ends of the plastic clutch line and slipping a reinforced rubber fuel hose over both ends and using some hose clamps. Then I was able to get back to trying to get my 4x4 linkage working. Anyway, what I found out after way too many hours laying in the snow in sub-freezing temperatures is that I couldn't get the transmission-side bracket to fit. There wasn't enough room for me to get the bracket over the studs without hitting the shifter housing that extends down past the tunnel panel. It turns out, which is obvious from the pictures but I didn't think of until I couldn't get things to fit, is that the Omix-Ada transmission x-member is a couple inches thicker than the stock unit. Instead of thinning out in the center where the transmission mount goes, the new unit is just a flat piece of metal all the way across, which eats up an inch or two of space under the tunnel. So now, instead of a marginal 4x4 linkage and stock plastic clutch line, I have no hope of getting 4x4 working for the winter and the temp fix is a ticking time bomb until I can get the parts in and have the time to replace the line. As always, one step forward and three steps back. Happy New Year!

I'm having a similar problem on my '91 HO. It seems to be worse when the outside air temp is colder. My guess is it's the coolant temp sensor, though I haven't gotten around to testing it yet.

Is it a constant squeal like a EEEEEEEEEEEEEEEE noise, a on off-on wee-ohh-wee-ohh that changes pitch/frequency with speed? If the former, I'd agree on the the cardan joint. Easy to test, just remove the driveshaft. Could also be the centering yoke gone bad, which is part of the cardan joint. If it's the latter, check the u-joints on the rear (since you say it sounds like it's coming from the rear. Removing the front will also help locate the problem, and jack the rear up, put it on stands, and let it run in 1st gear can help you pinpoint.

Sorry about that, I fixed the link. I ended up getting just a universal cat, 70317, and universal muffler, 13SC224 since I planned to rebuild the entire system. The important thing to note is that I am going with a single constant 2.25" system from the collector to the tailpipe, unlike stock which tapers down from 2.5 to 2.25 (and I can't rememeber at the moment if it's the cat or the muffer that does the conversion [edit] according to Eagle's post above it's the cat that has different inlet and outlet sizes) so these parts may not work for you. If you're really looking for stock replacements, I RockAuto looks like a good source (don't forget the coupon code for 5% off!), you can get the front pipe, cat, muffler, and tailpipe for pretty reasonable costs, or your local automotive store should be able to order anything you need if they don't already have it in stock. I've also got a spare header if you're looking to upgrade...

Some parts are in! My muffler fell off the other day so I've been running around with the cat as my only muffler and it's getting tiring. Hopefully taking it to the exhaust shop today to get some measurements. I think I'll be trying to go the Vibrant route and order the bends I need. Ideally I want to do everything in stainless with mandrel bends. Do it right, do it once. Anything less is just going to intstantly rust overnight where I live. I hate that front crush pipe with a passion but have read some exhaust shops don't like to bend their own due to clearance issues (and that you can smash the front DS against it if the position is wrong, among other things). Header is the Clifford 6=8 dual which I got the Y-pipe with and will be running a single 2.25" pipe the whole way. Muffler, cat, and tailpipe are from http://www.bearriverconverters.com (don't forget the coupon code, "Tacomaworld" for a big discount!). They were great to work with, immediately after my order they contacted me to clarify a few things that were in the catalog and to make sure I was OK with what I ordered. Nice! I'm not too sure on the tailpipe... it's kind of big but I couldn't find anything smaller that I liked. I was hoping to just find a nice dual 2.5" slash tip or something, but no luck. People want big honking tailpipes.

My tailpipe fell off and everything south of the muffler is quickly on its way, along with the muffler and cat soon to follow that I'm guessing. Been coming for a long time so I've been saving up for some replacement parts. Wondering what my options are for a DIY bolt-in replacement, if available (I think there's nothing though). Plan to do a few upgrades at the same time and want this to last, so I'm looking at stainless. Since it seems like I'll have to piece all the components together, I'd like to make sure I order all the correct parts and come up with a well thought out package. I thought I would start this thread with some common questions and expand on this with answers and any other tips, tricks, or mistakes I run into so that others might benefit. I have a header to replace the manifold, besides sending it out for coating does anyone have experience good or bad with the DIY alternatives? I've been thinking of going with this stuff: http://www.techlinecoatings.com/Exhaust.htm#blacksatin I've obviously done no research, do I need to remove the intake manifold to do remove the exhaust manifold? On my camaro, I went with Percy's dead-soft header gaskets and split-lock fasteners and am really happy, but nothing seems to exist for the 4.0. Are header gaskets a problem with these engines or would any regular pair from the parts store work? I'd like to just keep a constant 2.5" tubing the whole way. The bends in the stock system look horrible, they must pinch down to one inch in some places. Are there any stainless 2.5" mandrel bend tubes I can get for any of the sections (manifold-to-cat, or muffler back)? Any negatives to increasing in size from the stepped 2.5"-2.25" system on an otherwise stock HO? Has anyone bought and used successfully the "build your own" kits available from Summit or Jegs, that come with mandrel tubing bends of various degrees and lengths? From what I've read here, Gibson seems to be strongly recommended by a few people (sorry I can't remember who at the moment!). I have a pair of Dynomax SuperTurbos on my AMC 304 and they are pretty mellow, no droning, but with a nice idle that lets you know it's there without being obnoxious. That's what I'd like to achieve here. They seem to make a Superflow, Superflow CFT, and Race Superflow. What's the difference in sound between to regular and CFT versions? Any other recommendations? It seems like there is plenty of room available, should I worry about keeping the stock muffler and cat length for any reason (or go with something else for any reason)? My hangers are looking pretty rusty, and the rubber bits pretty cracked. Replacements (thinking Team Cherokee might have them) or good aftermarket alternatives available? I'm not sure what I want yet for the outlets. On my camaro I have the SLP TOTL system (two-out-the-left) and it's really grown on me. I might like to compliment that with a TOTR on the MJ. Any cool pics of various tips? Then again, I'm big into function over form and am also thinking a single 2.5" polished stainless straight back slash tip would look good under the JCR bumper... Time for some web searching! I will update this thread as I go along.

Here was my experience. No BFH needed. My reservoir moved about an inch forward so I did tap a new mounting hole for the screws, but that was it. viewtopic.php?f=2&t=32143

Did you get it? Any pictures? I think I'd like to get one, I'm tired of my cap (nice for the winter though). Great that it's a custom fit for the LWB or SWB instead of a universal.

Topless!

New tires. Sorry it's just a cell pic but I didn't have any free time before dark. Maybe this weekend since I hope to do a few thing.

I vote Aussie lockers, I've been DDing them for years and love it. I started with 3.07 gears and open front and rear, and eventually upgraded to 3.55 with Aussies front and rear. 2x4 with the locker provides more traction than I used to get in 4x4 with the open axles, and in 4x4 now it's just a monster. The gearing is great for a street truck with stock tires, or lets you go slightly bigger without killing your power. Mine click around corners. I have a straight front axle, no CAD. I don't have tire wear problems and the front doesn't lock unless it's under power. It's not a death trap on ice, I'm sick of hearing that. I've had some excellent winter cars ('85 Eagle 4x4 and '82 Ford Bronco II to name some great ones) and this is by far the best setup out of anything I've ever driven. I don't even bother putting weight in the bed, it doesn't need it. Because the wheels are locked, driving and slipping even are VERY PREDICTABLE compared to limited slips or systems with viscous couplings in the differential, if you know what you're doing. If you don't, go out to a parking lot and practice, because there's no magic 4x4 system that will replace experience behind the wheel in all conditions. No matter what system you go with, experience and comfort with knowing how it handles is the most important component to winter driving. Given your D35, I'd say go for the front first if you ever plan on upgrading your rear in the near future. Traction will be there when you really need it, and with the NP231 you can shift on the fly if you're in conditions where it's warranted. I wouldn't worry too much about putting one in the D35, if it breaks, just pull it out and put it in another axle.

I had my bodyshop do them, at the same time as they had to build inner rockers and do my full floor pans, so I didn't get too much info about the outer rockers specifically (I can tell you the bill was pretty hefty though :eek: ). From memory, I don't think they were terribly difficult for them to install (at least not compared to the floor), though they may have had to spend extra time at the cab corners. I do remember they test fit them over the existing rocker and nothing stood out as problematic. Should be nothing a competent body shop would be surprised to run into, or a home mechanic to tackle given enough time to examine. They look good, but not perfect OEM. You can see where the contours are not a perfect match, if you look. Good enough for a 21 year old truck I figure, but if you are looking for show-quality results be prepared to have them spend a lot of time on it.

Just make sure you get those alloy shafts in first! Wouldn't want egg on your face ya know?

Agree on that one, if you're just looking for a bit of height and it's going to be a street truck I'd upgrade the rear springs to the Metric Tonnes and the front to ZJ V8 springs (possibly with a 1" spacer which I am contemplating since my bed is empty most of the time and would give it better balance). That's what I've ended up doing on my '91 with stock tires, D44 w/3.55 gears and AX15 and it's a great street driver. 1st gear is very potent and makes hill starts easy. Check out mybuild thread! Might give you some ideas (or let you know what you're getting into!). Congrats on the MJ, looks pretty rust free.

What's that front bumper? I really like it. No cooling issues with the winch and three spotlights in front of the radiator?

Got a package today :D Were on backorder so these are fresh from the factory. Personally signed even! Nice welds. Paint's a little thin looking though in some spots. Should be a nice pairing to my HD crossmember I had to swap in to replace my swiss cheese stocker. Man, I should keep this thread up to date...

Wow. What a needlessly complicated system. I'm sure that had something to do with Jeep axing the CAD design. I can imagine many ham-fisted mechanics messing it up and owners complaining about things not working. Simple is better.

When mine went, you could hear the ratcheting working, it just wouldn't hold. I got a replacement so I could just do a swap and pass inspection, but when I took it out and examined it I figured it could be repaired with a file to make the edges of the teeth sharp again. Might work for a while, I never did try it out. I'm always cautious now to put pressure on the pedal prior to releasing so it doesn't spring back and scrape the teeth.

What kind of noise??

You don't want an HD clutch if you're using the stock fan. It will cool less effectively and wear out faster than the standard duty, for a stock application. "Heavy Duty" in the case of viscous clutches relates to the mass of the fan, the airflow, and the duty cycle. Go with HAYDEN Part # 2625. $35 from RockAuto. Testing procedures aside, you can usually tell by trying to spin the fan when the engine has been sitting overnight. Mine was frozen so bad it would slip on the belt rather than moving in the clutch.

Z&M stopped selling them?

For sure, weighs about 2-3x more too. I was a bit concerned about the 4 vs 8 mounting points but now I see it's totally not necessary. Wonder if the thing acts as a stiffer frame support too? Well thanks. Most days I feel like giving up and just throwing in the towel and am disgusted at how much time and money I have dumped into this thing. Really, this little bit was nothing after just about everything else I've had to fix. And I should have know better before tackling the project as this was one of the last virgin bolts I hadn't touched yet, so I really wasn't thinking when I though it would be a quick job to swap the transmission mount. I figure now that if I knew everything I would have to do before I made the purchase, I would have passed it over and bought a truck in better shape (when your spring mounts look like swiss cheese... :eek: ). But it's been slow and steady progress. There's really nothing too it, you just have to have more money than sense, as a regular person would have bought a perfectly nice Ranger or something and not have had any of these problems.