azscott

I have an 89 MJ 4.0 4x4. What is useful off of an 86 2.8 v6 4x4 MJ form a mechanical standpoint. Someone is selling one with a blown motor for 300.00. ...besides doors...interior stuff...anything else from a drivetrain that is worth it? scott

...yah I may just be getting too anal over it. In reality..it isn't an issue. It started out as one of those things I figured I would fix as I went along...try a little of this and a little of that....and then...somehow it became an obsession to figure it out. Since the DRB says everything is fine...I will be happy with that :cheers: Besides...I have a Peugot Tranny in it with a fuuny revese gear....I gots bigger things to worry about soon. :eek: Thanks guys Scott

Yah...missed that link for the sesnors.....I have alot of stuff bookmarked but not that one...so it is working fine. Well thanks for pointing that out. 'Well...that is one piece of good news. The bummer is...what in the heck is casuing this stubborn idle problem. As it warms up the idle will climb from 600 to around 1050 when warm. Sort of the opposite of a cold engine I would think. usually they start high and will drop in idel RPM's. I am missing something simple I think. On the oether hand...it runs fine overall and maybe for a 20 year old engine...I should not worry... :D scott

...the other possibility is that the O2 sensor and related wiring is fine....and it is sensing a rapid change in Air Fuel mixture. There is a kind of cycle that I can follow with the engine idle or sound. When it cycles back to Rich...you can hear the engine idle change. SO whatever is happening with the O2 sensor or levels is affecting the engine idle. Now I disconnected the O2 sensor and ran it like that for a minute...just to see what i would see. It did not change how the idle would change....the only thing i saw was the O2 sensor display would cycle between Open loop...closed loop. May be normal with a disconnected O2 although I would think it would lock out in one mode or the other....although I have no information to support that. scott

Well if you read the Renix fuel injector manual it only ignores the O2 during crank mode. During warm up, Idle and so on it recieves input from the O2 sensor. The manual states...in warm up mode proper pulse width of the injector is determined by inputs from CTS, MAP, MAT, TPS ESS and O2. It certainly uses it for idle mode as that is clearly stated in the Renix manual. During idle mode it uses the O2 to establish proper air fuel ratio. Now wether or not it would cause any idle changes I don't know for sure...seems like it could....but would it...don't know. At the least it is not right. The ECU uses the O2 to ID wether it is lean or rich and if it is cycling then it should stand to reason the ECU would counter the wrong condition until the O2 cycled back to the correct condition. So in the least it has to be dickin with the ECU trying to maintain a proper Air/Fuel mixture. I would think? All the other sensors are within range and stable. The IAC was replaced at the same time as the O2 and neither made a difference. The IAC is getting the variable voltage from the ECU. As for difference when it is warm or cold...I will check. Are you asking about difference in idle speed or O2 sensor. As for idle..it does not matter too much what temp the engine is at...although mAYBE a little more twitchy when cold....actually may idle a little higher when warm..but hard to say...it seems to wonder at times. Other than that it runs great. Certainly accelerates fine and has never stalled. scott

First off I don't have the powertrain manual that has the section on how to test the O2 with the DRB. However there are not alot of options in the DRB anyway. Second i just replaced the O2 sensor last week...symptoms are still the same...idle is erratic ranging from 600-1100 at times....it does not lope..rather it will either be one or the other. During idle, if I select sensors on the DRB and watch ALL of the sensors they all are acting correctly and within range ACCEPT the O2. The O2 sensor is cycling quickly between .5 volts (rich) and 4.5 volts ( lean)...and it does this erratically and rapidly. It even does this at higher sustained RPM's. I would assume this is the source of my issues as the O2 is a key sensor in the ECU deciding if it is in a rich or lean condition and if it is bouncing around rapidly and constantly it will or should cause what i am seeing. Of course the questions is....why is it cycling. I doubt it is the O2 sensor...although I have the old and can hook it up and see what it reads even without it being installed in the down pipe. My guess...and yours probably...freaking wiring problem. :fs1: What say ye all. scott

...ahhh....gotcha. Yah I heard similar issues with ones off Duh-bay. I waited until atleast i saw one that was not trashed to heck. Still I was a bit uneasy until it arrived. Actually ...once I get the issues with mine resolved and running right I will probably sell the DRB and Adapter. I really did not have extra cash to buy it but figured buy it...diagnose it correctly and sell it off for my cost. Break even in the end and get her fixed right.....is worth the money. scott

...well I know it will do Renix 4.0 now. I am not sure if it HAS TO HAVE the superchip installed...but all the ones I see have them in anyway. I do not know what extra vehicles the superchip adds verses without it. I am sure you already know but it is the adapter that is also need for the Renix jeeps. I will play with it more tonight...I want to do the sensor tests tonight if I have the time. I ran out of time last night. scott

I picked it off of Ebay. i waited until I could find them in good condition ( most were trashed) I had to buy them seperate....DRB II from one seller and Jeep Adapter from another. Both are in very good condition. I paid about $350.00 for both plus shipping which was not much extra. DRB did not have instructions however the unit walks you through the tests. I am tired of shotgunning sensors replacements...I could have simply bought these two at first and broke even at this point:-) scott

...well maybe it is not supposed to be. It does plug in. It has the Renix 4.0 engine for 89...but only listed under the Cherokee? It did run through the engine test fine...it prompted me to do all the idle tests etc and never had an issue? I have two OEM service manuals and they call out the DRB II in the tests. scott

...I picked up a DRB II with Super Chip plus the Jeep Renix adapter. Reason is I am tired of chasing my @ss over this low idle issue and figured atleast with this I can run the sensor tests and engine diagnostics.. I hooked it up last night and tester worked fine..even ran the engine diagnostics...engine tested fine. That was all I got to before my teenagers ruined my night. My question is this. Uner the 89 jeeps there is no MJ 4.0 listed. I chose the 89 XJ 4.0....and would ssume since it is the same Renix engine it should be fine. This was the engine I chose when I ran the diagnostics and it tested fine. Anyone know for sure if this is correct...there is no MJ on the DRB II and so it is fine to use the XJ 4.0 Renix mode? I am going to test the sensors tonight....especially the TPS as the the Renix manual I have does not use the .8 volt method for calibrating the TPS so I am going to use the DRB which the manual states is the preferred method. scott

I will take a look at that. However I don't think the low idle/rough idle is related to the compression. I say that because it is intermittent. Sometimes the idle will be a little high...sometimes normal and alot of times low. It does not range over a wide range rather from 400 rpm-1100...which is wide I guess but not like it goes up to 200 or so. Usually it runs 500-800. I think there is either sensor that is failing...or maybe faulty wiring...or? If it was compression it should be consistent and not come and go. I do have to replace the knock sensor as it is physically broken. The plastic cover cracked in half and I had to glue the whole thing back on. Although on or off the truck did run any different....which could mean that sensor is not working at all..? I ordered one from Napa..which is a generic replacemnt it looks like but won't be here until Wednesday. scott

...hmmm...that was in the back of my mind too. I don't have anything to read compression at the moment. If that is the case...I would live with it. The PO did...he had a piece of metal glued to the throttle stop to adjust the idle...hah!. I hate jury rigging...but I may not have a choice. I know I am getting some blow by as I am getting oil back out the CCV intake. Well..heck..it runs good enough...I may just have to put that metal shim back in and move on..:-) Been working on the Mj all weekend...time to take a break.....until next weekend. Scott

Upon reccomendation I tested the fuel pressure at the railllfor the hard start/rough idle...etc. Pressure is 34 psi.....now it will hold that pressure for about 45 minutes before it starts to drop slowly...after an hour it was about 20 psi. Oddly...or not addly...the pressure did not have anything to do with the rough idle. I let it sit for 10 minutes..started it...and it idled rough for about a minute or two. It revs up fine just idles very low and rough. Pressure on the rail was still at 34 PSI. Let it sit for 45 minutes it had dropped to 20 PSI and is started fine. Now it still idles low..changed the O2 today... still no help. To me...it is running rich...if I had to guess. Which makes sense as I know the PO had changed the Cat a while back and this may be why. Driving me nuts..all the other sensors tested o.k....changed the IAS..no help. Adjusted the TPS no help. Fixed all the VAc leaks on the intake side..no help. Hate to take it into the dealer...but not sure what else at this point. Of course it is 20 years old so..? scott

..yah I know...I expected some...just caught a bit off gaurd as to how many and how big. I am surpised anything that ran off vac was even working...I had some monster holes...I am sure you guys have seen them for sure...I am just shocked at the amount. Especially when the PO kept telling how good of a Jeep guy he is...yah.....well....I think not. Thanks for the help guys. I think I have half the leaks found....the rest are gonna be a bugger. scott

...man....I got leaks EVERYWHERE....I fixed like...7 so far. Most are in what i guess i could call accesory vac lines. These are the hard plastic colored vac lines. The small hard plastic vac line coming from the football had 2. There is a small hard plastic red line that is T off the larger rubber line that comes INTO the football...that had a few leaks. The pink line going into the canister by the Distributor had a couple. Still...it is loosing vac as the AC still changes over to defrost under hard acceleration...although it is somewhat better. There must be freakin leaks everyhwere in the small hard plastic lines but I can't trace em all. They either go through the firewall and behind the dash or some under the truck. There are no leaks in the main engine lines as I replaced those...easy to get to. Man what did I get myself into...? scott

I can check that. But wouldn't the problem be worse when it sat overnight if theere was a fuel pump pressure problem? Or am I looking at it wrong. I will pick up a fuel pressure test kit later today as I wanted one anyway. scott

yah kinda figured. If the leak is over by the footbal would it still affect the idle with TB sprayed on it? Certainly no surprise if there are multiple leaks due to the age of the lines. I replaced a few in the TB and the CCV. I need to look at the brake booster...I think that is vacuum too and the gasket at the check valve was cracked. Oh well...guess I have something to do now this weekend anyway. I wouldn't be surprised if the other idle issues are all related to vacuum. scott

Yah that was my next question...I actually logged back on to ask that question as it would seem to NOT BE NORMAL....!! Maybe this leak is causing some of my other issues. What is a good method of testing for a vacuum leak over there. it is easy in the CCV lines or anything near the TB as Tb cleaner sprayed on the lines will show a leak real quick. Would the old soapy water thing work on vacuum lines? scott

Arghhh...had no isue the first month...now....? The last couple of days it has been a little hard to start. Sometimes it will start ...idel rough and then stall. Or just idle rough for 2-3 minutes. It accelerates fine...but will stall or almost stall for the first 1-2 minutes on startup?. Seems to only di this if warm or hot. When it sits all night no problems starting...so far. If I stop for 10 minutes or so and get back in it is more likely to do it....although sitting for an hour or two will also. Runs fine other than that. I checked for vacuum leaks but that should cause a high idle I would think...but anyway...none were found. TPS was adjusted a month ago but it was fine as was the other idle thing next to it( name escapes me. MAP seems to work fine and tested fine. I still plan on replacing the O2 after some recoomendations for the low idle as I have no ideas left on that. But now this hard starting/rough idle for the first 2 minutes it starts has become an issue all of a sudden. What would be the logical approach to this. I love the truck...runs great overall...even with the Puegot tranny ( hey what can ya do. again this is an 89, 4.0 5 speed. ( I will put that in my signature shortly) scott

[ Yah...what you said. I checked it again...that is what is going on. Makes sense now...kinda like my old ford...with Vacuum wipers. Accelerate hard...and watch the wipers die.

It is a 1989, 4.0, 5 speed. I thought maybe vacuum but was not sure...and so kinda blew it off. What may be happening is two issues and I am correlating them as one. First the fan does just randomly shut off...and if I tap the AC/Heater controls it will pop on. Come to thionk of it...when it does THAT it shuts off instantly. With the 5th gear thing I though I could hear the motor running but could feel the air slowly dying. I never checked the defrost. Although..now that you mention THAT...I did try it with no AC in heat with the defrost running and it did not do it....so I guess that answers that. SO I will assume the vacuum thing is to be expected ( as long as there is no Vac leaks)....and the fan suddenly stopping randomly ( which I can rap on the HVAC panel and make it come back) ...is still my only original issue. I just combined the two. As for the IAC...I thought I read there was one on the 4.0...I could be wrong...and I could have it confused with my 87 Pathfinder.....it happens. scott

First....I have been fighting a low idle for a while now..still have not fixed it. Does not stall although it will hover around 500 rpm which makes me a nervous in traffic. Last recomendation was change the O2 since the rest of the components that would affect it are fine or have been changed. But....there should be a sensor that kicks up the idle when an electrical load is sensed...such as the AC. When I kick on the AC the idle does not bump up and it should like....40o rpm or so. Who knows where the sensor is and what it is called. I know i read it on here somewhere but now I can't find it. Second question si related to Ac Fan motor. It has been stopping or slowing down randomly. No big deal..usually it is a resistor in the speed control...if I can find it. The wierd thing is this. If I am tooling down the highway in 5th gear and start to accelerate the fan slows down and slowly stops...let of the gas and resume a normal speed the fan speed returns and ....it does this regularly....and only in 5th gear...which makes no sense. Does not do this in any other gear on a regular basis. Sometimes it will just slow down or stop and then a few seconds later it will speed back up but it is random. Not in 5th gear at say 60 mph. Slowly accelerate and the fan speed always slowly dies...let off the gas and resume a light accelerator pressure to stay at speed and the fan speed resumes. That has me a little stumped and wondering if it is more voltage related...regulator...alternator....I have no clue. Anyone have a thought. scott

I would add that I think you could use a foam roller with closed cells and the stucco appearance will reduce a bit...I think. The rollers that they sell are a blue large open celled roller..very stiff foam with large pores much like a true sea sponge. The large open cells are what cause the material to pull up and make the stucco appearance I am fairly sure of. The material has a consistency of very runny grits or Farina cereal...which is the best comparison I can come up with. It is NOT lumpy...rather fine gritty...well actually it is fine rubber grit it looks like. SO I would assume the stucco lumps come from the style of roller. I may try and find out as I have a bunch left. Certaily it is NOT for everyone....once you put it on..it is there for life. You are not going to remove it once it is on. But for applications where someone wants a decent unique look on a truck that maybe they can't afford nor want the expense of a full paint job it is a unique alternative. I will say i like a bit better after the gloss fades a bit. Even with the Uv protector the gloss will fade off and becomes more of a satin look...which is better I think. scott

How much does a can of that roll on bedliner stuff weigh? The weight is minimal. There is probably 1.5 gallons of product on the truck. Fugure a gallon weighs about 11 pounds so a gallon and a half is 17 pounds....so about that much.