buckwheat

Cruiser, I have not done Tip 14. What I did is turn the screw all the way out (meaning the butterfly was closed) then screwed it back in until I heard the engine rpms pick up very slightly. I will go back when I get a chance and do it your way. The problem is mostly fixed right now. It seems that I had 2 bad IACs in a row. I put a third one in and my idle is mostly fixed. Recently I have had problems with it stalling as I start in first gear, and with it jerking as I drive along at low rpms. By jerking I mean it feels like a carbed vehicle when the fuel line is partly clogged. It surges forward then stalls for a bit, then surges forward, then stalls, but in very rapid succession. So I think my next thing is to check fuel pressure and see where that is at. But it is much better than it was, and is back to being my DD. Thanks for everyones suggestions. I wanted to make sure to post my solution to the problem in case anyone comes across this thread in the future.

Alright, did some more work on it today. I looked up the vacuum diagram for the Renix 4.0 and noticed a lot of mistakes from the PO. Got those fixed. Then realized the EGR had a hole in the diaphragm and wasn't working. Got a spare one from a 90 Jeep Cherokee parts vehicle I have sitting around. Neither of those two things changed the idle at all. Then I cleaned one of the IAC motors and was a little more forceful about it. Not rough, just put more elbow into cleaning it. Swapped that in. Perfect idle, right at 600-700 rpm. Stayed that way as long as it was parked. As soon as I took it for a test drive the idle became erratic. Meaning that sometimes it would idle perfectly at 700 rpm. Sometimes it would idle too low and die out. Sometimes it would idle higher at 1500 rpm or 2000 rpm. There did not seem to be a rhyme or reason to it. I have ordered a new IAC from Orielleys. In the meantime I have a third IAC I can grab and put in the truck. Right now my thinking is that the last two IACs I have tried are both faulty to some degree. I know that mathematically the odds are slight, but they are both used, so it is possible. Anyone have any other thoughts or ideas for me to try?

Knucklehead: Thanks for those ideas, I will be sure to check out the vacuum canister and the CAD connections. FPC: Its good to know that I have a possible temporary fix if I can get it to idle normally once more. I will also make sure its not an IAC problem, although having tried two different IAC's one would think the problem is elsewhere. Keep the ideas coming if you got em. I will report back on these possible fixes as soon as I can get to them.

Sprayed Mass Flow Cleaner spray (highly flammable) around the intake and on all vacuum lines. No change to idle. Checked the top bolts that hold the intake to the block, and they seem to be very tight. I'm running out of ideas quickly. Any thoughts would be appreciated.

My 87 MJ 4.0L has yet another issue I can't seem to track down. Extremely high idle. In the 2500-3500 range. So far I have tried without success: Adjusting TPS to spec using Cruisers Renix Tips. Cleaning IAC Cleaning TB Pulling a TPS out of another Jeep and adjusting it per Cruisers Tips. Has the same problem. Pulling the wires to the TPS and running it without them. Has zero effect. Changing out the IAC. I accidentally started it with the MAP sensor tube unplugged from the TB. The idle was around 1500 and seemed to stay there. Not sure if that is at all related. I plan on looking for a vacuum leak by spraying everything with throttle body cleaner when I can get a can, but I wanted to make sure I wasn't missing something simple in the mean time. I searched and read quite a few High Idle Threads, but none of those solutions seem to work for me. Whats got me stumped is why would the high idle be there after pulling the TPS wires. Shouldn't that tell the ECU to use some default setting? Thanks in advance for any help or advice.

I made an account on http://www.cherokeeforum.com/private.php and sent him a PM. Other ideas I wanted to bounce off of you: CTS: How can I test this when I can't get the truck up to temp? I know it controls injector pulse and ignition advance, so if it was bad and reading infinite resistance that could cause my super rich and rough condition. And where can I get a replacement at? MAT: Same questions as the CTS. How to test, could it be my problem, and where can I get a replacement? Injectors: I found the following site http://www.injectorwarehouse.com/injectors/volvo/mp5060.htm for the injectors. But that seems kinda pricey to me. What do you think?

No. It runs rough the entire time. Cruiser, injectors was the next thing I was gonna try. But I am not having any luck getting ahold of programbo on cherokee forum. Is there another place I could get the Volvo 746? If I am replacing them, I might as well do an upgrade.

Do you mean the where the wires plug into the ECU unit in the cab? I have already taken those connectors apart and cleaned them. I have also tried putting in a new ECU from a 90 jeep cherokee. I had the same issue with the new ECU that I had with the old one. It made no difference.

Cruiser, That would make sense if the problem was new. But I had the same issues before I got rid of the C-101. Trying to fix the problem is why I bypassed the C-101. It just doesnt seem like the causality works right for me to have the same issue before and after AND it be related to my solder joints. Not saying that they are good joints, it just doesnt make sense to me. What I'm wondering if why disconnecting the wires on the MAP sensor will raise the RPM by 1000 and make it run smoother for 2 seconds, followed by it getting rough again. Is that a normal thing when you disconnect the MAP wires?

So anyone have any ideas on what I can check or try next?

Tip 5 done. Got a steady ready of .9 ohms.

I have done the Sensor Upgrade by bringing the six brown wires together and soldering and shrink wrapping them. Tomorrow I will look at the ohm reading and see what it says.

Sorry its taking me so long to try these things. Everything gets busy around the holidays. Also the wife decided to put gas in the diesel truck and drive it till it died. But for now I am back on the MJ problem. Distributor is indexed, no change. Other things I've noticed: When I pulled the O2 sensor plug apart while the truck was running nothing changed. Sounds really rough and has no idle If I pull the wires off the MAP sensor while it is running the rpms will go up by about 1000 and it will even out for 2-3 seconds. Then the rpms will drop and it will go back to being rough. If I manually move the EGR valve it will choke the truck out. Is this supposed to happen? Any other ideas or paths to send me down? Thanks so far to Cruiser for his suggestions.

I don't really understand #13. If the rotor is at the #1 post when the engine is TDC, isn't that exactly what we want? Why do you have to remove the distributor, and what is happening here: "Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw. Remove any burrs and metal filings from the distributor."? Not that I don't believe it needs to be done, but I would like to understand what I am doing first. Thanks for the help so far!

Alright. C-101 bypassed. Truck runs no better than before. Still sounds like its missing on multiple cylinders / timing is off. And it still has no idle. I have to put the pedal to the floor to start it, and if I quit feathering the gas while it is running it will die. While running and feathering the gas it is running VERY rich. I can smell raw gas from the exhaust. To this point I have: Eliminated C-101 Changed TPS from a known good vehicle (haven't calibrated it because I can't get it to stay running) Cleaned TB Checked CPS Changed out the ICM and Coil from a known good vehicle Changed spark plugs Changed MAP sensor and vacuum hose from a known good vehicle Checked spark at each plug These things are not in order, but I have tried them all. Everything looks good. So to me it seems like a timing issue. Is it possible that my ECU is bad?

So I have been (slowly) working on the C-101 elimination. I have the first row of wires looking down at the C-101 soldered and shrink wrapped. However, below that there seems to be wires without matches on both sides of the connector. I was under the impression that every wire had a counterpart on the other side of the connector. Is this not the case? Kinda worried I've screwed myself somehow. . .

Thats what she said. I apologize, but I had to say it.

I was reading your tips and thinking that the only way to be sure the C-101 is not an issue is to eliminate it. Are there any downsides to eliminating that connector? And is it really as simple as taking one wire from opposite sides and soldering them together? Plenty of slack in the loom to manage this correct? I hope to get to it this weekend. *fingers crossed*

My 87 MJ 4.0L BA10-5 has decided to have its first major problem. I figured it was time to clean the C-101 and ground at the dipstick. Took both apart no problem, wire brushed them till shiny, sprayed with brake cleaner, polished some more, then stuck them back together. When I tried to start my MJ to back it out of the garage it would crank but not catch and run. After playing around a little bit I realized I could floor the gas pedal and it would start and run, but VERY rough, like it was missing on multiple cylinders. Also, if I quit feathering the gas it would idle down until it died. The exhaust was also very rich, smelling strongly of gas. I pulled my spark plugs and the back three (closest to the firewall) were black. So I replaced all 6 with champion copper plugs, but that didn't help. I checked my TPS and it was properly adjusted per Cruiser's Renix Tips. I have looked over all the vacuum lines and can't find anything that appears to be out of place or missing. I changed my MAP sensor from a known good vehicle to this one, as well as the vacuum line on it. No change. I unplugged my O2 sensor and tried to start and run it, again no change. The vacuum line to the fuel pressure regulator doesn't seem to smell like gas (hard to tell with the exhaust being so rich). I have tested the CPS and while cranking it would read .75-.8 AC volts. I thought it was only supposed to read .5? Is this an issue? I plan on renting a fuel pressure gauge to see what it is at with the key on. I also will check to make sure I have spark on all cylinders. Does anyone have any ideas or recommendations of other things to try? Could I have messed something up cleaning the C-101? I'm really at a loss, any help is appreciated.

Alright, I am still having issues with this. OnlyinaJeep726, thanks for reminding me about the MAP sensor. Nothing was wrong with it, but it is good to check anyways. The Problem: Truck will start, but I have to put the pedal to the floor to get it to catch, and it runs horribly. Sounds like it is missing or not timed correctly. Also it will not idle. If I take my foot completely off the gas pedal it will run slower and slower and then die. Obviously I had none of these problems before messing with the C-101 and valve cover. I have checked: The C-101 to make sure none of the metal tabs were bent or misaligned. Everything in the connector looks good now. The CPS also tests fine. I have spark (hillbilly test of holding the tip on a piece of metal and watching it spark), and while I have not tested fuel pressure at the rail, it seems like pressure is not an issue since it will run. I have also cleaned off all grounds in the engine bay. I was trying to trouble shoot in my head and figured it was the perfect time to clean up some grounds. What should I look for next? It should be said that I am a complete newbie to mechanical work. Everything I know about my Jeep I have read off this site. So thanks for the help, and sorry if I am a bit slow on the uptake.

Thanks for all the replies. I definitely have more money than sense sometimes. But the cover was already bought, so no use trying to backpedal. I was able to get it in place and the bolts all torqued down. I used an inch-pound wrench to get it to spec. While I was under the hood and waiting for some replies on fit I decided to clean my C-101 connector. I got everything situated and put back together, hopped in the drivers seat and tried to start it: bad backfire and then cranking without catching. So one problem down (the valve cover) and a new problem pops up (no start). Is there any way that I messed something up with cleaning the C-101? or could something have gone wrong while the valve cover was off? It was dark so I haven't checked much. Planning on looking at the CPS and doing the ICM and Coil Contact cleaning. Anything else that you all can think of?

That was less than helpful. I need to get this thing up and running for work on Monday. Anyone have any comments on fit? Will it work or not?

I have an 87 MJ with the 4.0 engine. It has been leaking oil from the valve cover and airbox. I read a few threads where people had put on a new valve cover with the felpro gasket to cure both these problems. I looked in the local junkyards, but couldn't find a Cherokee that would work. So I ordered : Dorman OE Solutions - Valve Cover Part # 264-983 Link: http://www.oreillyauto.com/site/c/detail/DOE0/264983/02395.oap?year=1997&make=Jeep&model=Cherokee&vi=1180370&ck=Search_valve+cover_1180370_201&keyword=valve+cover I thought it should work since it replaces 97 Cherokee valve covers. However, after looking at everything I am not sure anymore. The depth will be tight on the rockers, and the nuts on the head bolts are hitting the flange on the cover. So will this work? Should I try and modify the cover to make it work? Or will I be better off sending it back to Oreillys and getting my money back?

I would love to get a front and rear axle for my 87 MJ with 4.10 gearing. Ideal would be a Dana 44 for the rear and an XJ 97-99 Dana 30 for the front. But I will consider all options. Only possible issue is I am in the middle of Missouri and don't want to spend a fortune on shipping charges. So if you have something that would work for me (hopefully within reasonable driving distance from 65340), let me know. Thanks in advance!

My 87 had the same issue you are describing. I eventually replaced the harmonic balancer (after replacing all the other pulleys) and that fixed it. So I would at least give your HB a visual inspection and look for separation.