Maybe it's not manly, but I use Vasoline Intensive Care hand lotion, especially in the winter, or my knuckles will crack. After it soaks in, wipe them with a towel or something to get rid of the excess. I can't work with gloves, even mechanic's gloves. There are many things to wash your hands with, but what works for me is Boraxo Powdered Hand Soap. It's cheap and does the job. I use a brush around the nails.

Go to the junkyard and get an injector, stick it in #1 and see if it works. If it does, keep it or put a new one (or set) in. Don't go replacing the coil pack until you check out the injector. I would still replace the insulator boots.

 

I really don't have a junkyard anywhere near my location that I can pick around on. Is there a way to test the wiring with a multimeter? My understanding is there is constant voltage supply to one wire and a ground pulse on the other that activates the injector. I switched thr injectors at one point and the problematic cylinder did not change BUT the good lord and baby jesus know that I have been wrong before. I'm going to do some more digging this afternoon on this.

On the ignition side I found this video.

Https://youtu.be/Sk_8TKMwyPo

I'm going to attempt this also. Just need to find something long and conductive that I can ground with a ground strap.

The last thing is that damn CPS on the left side of the block. If all else fails what's another 100 dollars right? LOL

 

I tested the ignition coil just now. I made a wire with an alligator clip at each end, connected one to tip of plug and the other on ground connector. I have spark on #1... I have switched injectors before but want to do it once more just to be sure (and because I am OCD) later tonight. Also I checked the OBD codes and sure enough: p0201.

IF it is narrowed down to wiring.... is there a continuity test I can do from the connector to computer to the injector connector? I guess I need a wiring diagram that is accurate with my model. I can get a connector for like 12 bucks and I know how to solder.

 

Another update. I thought for sure I would end up finding a wiring problem from the PCM to the #1 injector... i found a pinout diagram applicable to my model and tested continuity from the PCM connector pin to injector connector #1 and it tested okay. So if the wiring and injector is good that would narrow it down to something on the other side of the PCM right?

When this started happening I got both a P0300 and a P0301. The 00 code means that there is a slight misfire across all cylinders and the 01 is a SERIOUS misfire on 1 right? All of this started abruptly one day and was not gradual. Other than the misfire on one cylinder everything else seems great. Can a camshaft position sensor cause this issue? Everyone goes on and on about "before you spend the money on that, try this first"... Well folks I think I might be out of stuff to test.

I go out of town tomorrow for the weekend so I have this evening left to mess around with this. Anyone have any suggestions? I'm starting to feel like if I am still dead in the water next week I am just going to take it to a mechanic. I just lack the testing tools.... More than likely a seasoned professional can tell me right away what it is by looking at it and taking some measurements and readings. The damn thing has been out of comission too long for me.

 

It could be a cracked solder joint on the terminal strip inside the PCM. All the PCM does is ground that wire from the injector to fire it. The ASD relay supplies the power. I would check that before I replaced the PCM. With the engine running, backprobe the injector connector to see if you're getting a cycling signal. (flashing light)

 

I'm spreading my posts out a bit now. Mainly keeping updates in case anyone else in the future is in the same boat that I am. I got to thinking. I never went and took my vehicle on the highway after the misfire started happening... I guess I was scared to. I found that while in drive and under load, if I gave it some gas and opened the throttle it will bog down and started backfiring through the intake. By now the misfire has gotten a little worse and you can really feel it at higher RPM. I got a P0152 and P0051 after putting everything back together so I figured my 2nd upstream o2 sensor connector got messed up when I was disassembling everything. The error code showed "high o2 sensor voltage" so the PCM was already cutting back on the gasoline thinking I was running rich. I was hoping that was causing these problems. I changed it out and it helped.... but I am still having the misfire. Consistently cylinder 1. I had changed the fuel injector connector with no luck.... I guess my next steps are to check all 6 sparks on coil rail at once. When I checked for spark I just checked the one cylinder.... Maybe the coil rail is having trouble handling all 6 sparks. Just have to rig up something.

I have been pondering. Right before this happened I changed my water pump. It might have been literally the next time I drove it when I noticed the problem and got the flashing check engine light. Now that I have reset the PCM after changing the head gasket and getting all that work done I have not gotten any misfire error codes but it is obvious I am still misfiring on cylinder 1.

I have found a couple vacuum leaks. I have fixed them and I have had no difference. The previous owner backed into something real hard and I have a huge dent on my rear driver's side bumper that was never fixed. It triggered a check engine light for the evaporator canister (the one usually triggered by a loose gas cap) and was going to cost me 1000 dollars for the auto repair folks to fix. Of course I cheaped out and found a crooked auto shop that had a way to do state inspections with a check engine light on with 100 bucks cash. I did that for 3 years or so while I lived in Dallas and now I live in a county with zero emissions regulations so I haven't had to worry about it. I wonder if maybe a vacuum leak got worse or something? This problem happened very abruptly and wasn't gradual. I really don't think this is a vacuum leak problem but I am always wrong. I guess some charcoal canister is back there that does something?

I understand that backfiring through the intake is the result of running "lean" which would point to a fuel issue. I am sure this fuel pump and filter is factory and I am literally 158000 miles right on the money. I rolled over to 158001 while driving around testing different scenarios. I need to get my hands on a fuel pressure tester.

The cats are stock also. No rattling or obvious cat symptoms that I can tell (with my zero automotive experience) but maybe this misfire has exacerbated any cat problem since a flashing check engine light is indicative that a misfire condition may cause cat problems if you continue to operate with them.

I need to check the timing... I am dreading this because I have to remove this pain in the *** radiator fan shroud. I think I will cut it in half and rig it up in such a way that is easier to remove next time. I left it on the whole time I was doing all the work on the head for this reason. With checking the timing I can check the cam and crank sensor data if I had a computer to hook into my jeep. Someone in this thread at some point mentioned using their phone as a reader? I found this online...

http://actronuscan.com/

The thing is about 80 bucks and does all the readings that can test a cam and/or crank sensor. I'm thinking about buying it. God knows that every time I have a problem I will drive myself absolutely nuts trying to fix it myself before asking anyone else I know personally for help.

The last thing I wanted to bring up is the lifters. Dave, you suggested to change them out earlier in this thread. I read a bunch of crap about not changing them out without changing the camshaft also... It spooked me and I blew it off. I wish I would have checked them for damage and signs of sticking and cleaned them instead. Live and learn.

I'll post a new update next week. Happy new year!

 

As a general rule of thumb, you can run new lifters on an old cam, but not a new cam with old lifters. The reason for this is new lifters are flat on the bottom and will wear dished because they are mounted off center to the cam lobe so they spin, allowing the wear to be distributed evenly on the lifter. A really old cam may have been worn rounded on the edges of the lobes if the lifters are too worn. You can see this by looking down the lifter hole at the cam and inspecting the lifters. As long as the cam lobes are not worn rounded, new lifters will work fine.

With a new cam, the lobes are perfectly flat and if run with dished lifters, both the cam and the lifters will wear fast. GM had problems in the mid 70s with "soft" cams in the 427 engines where one lobe would wear out quickly and cause the valve to not open fully. This created a loss of power in that cylinder and the cause was hard to find. IDK, but I've never heard of jeeps having cam problems like this.

I don't think your timing is off unless you removed the cam sensor when doing the head. The PCM adjusts the timing with sensor input and as long as it was right before, it shouldn't be wrong now. Also, if there was a problem with fuel pressure, it wouldn't be with just one cylinder.

Did you replace the insulator boots on the coil pack? You said the #1 boot was soaked with oil. That could have created a carbon trail thru the rubber to ground out the plug. No amount of cleaning will change that. Backfiring thru the intake can also be caused by crossfiring on an open valve. The part I don't quite understand is the coil pack only has 3 coils and 3 drivers. It must fire 2 cylinders at a time, one on compression and one on exhaust.

 

I did install a set of new boots and the little springs that push down inside the ignition coil. A few of the boots were swimming in oil but I still get the same thing now. The lack of effective ways to check the ignition coil bugs me... I am going to come up with something to check all 6 at once.

I didn't remove the camshaft sensor while doing all this. I did however remove the cap yesterday to look at it. There was some oil that climbed its way up into it but not on the electronic connectors or anything. It is actually an extremely simple part. I'm agreeing with you on the timing thing. Or at least being hopeful... Mostly because this problem just came about one day and was not a gradual thing as if my timing chain had worn.

I guess I should do a compression test. I have a couple mechanic buddies that came and helped me put the head on. They both felt inside the piston walls with their fingers and said they were surprised at the lack of wear on them considering the mileage I have. The most worn cylinder was #6. No odd wear or vertical lines in the pistons but still possible there is a piston ring problem?

There are videos of folks repairing the PCM on youtube. There is a problematic area inside where contacts to an internal socket become undone and have to be resoldered. One of the ways I make my livin's is repairing defective computer and laptop motherboards SO this is one thing that I can hopefully avoid screwing up if it comes down to this. Whenever I removed the three harness plugs from it a little less than a week ago I noticed the black one (or whichever is nearest to the engine) looked like it had gotten some moisture on it at some point and shorted out. There was white buildup on the base of some of the pins. I checked out the pinout diagram and I never had any problems with anything feeding off of this area. I suppose that doesn't mean something internal didn't short out or finally take a **** on itself.

Going to have a weekend of reflection while out of town visiting family. I am going to pick my uncle's brain while I am at his house. He is a masterful Mac and Volvo diesel mechanic with 30+ years experience and the go-to guy for anything electrical. I wish I could just take the damn thing to him....

Edit: snapped this nice little pic. Going to have this thing running as good as it looks soon. Please ignore the hose thing I have going on from valve cover to cold air intake. The little plastic nipple broke off and I haven't gotten any JB weld to put it back on yet.

 

Sure looks pretty! Nice job.

I saw a guy who took model paints (Testor's) and a brush and painted the letters of "Caution Fan" with international orange. You could do the "Jeep" and the "4 liter" also.

 

Just got back into town! Man I hate road trips. Even short ones....

I talked to my mechanic uncle. Went through the whole series of events from start to finish without even saying what I thought it was or what it might be. He said right away "sounds like a coil pack. If not that, the PCM. More than likely the coil pack though." I told him I had spark on the single one when I tested it and went on about how there is a way to ground out the threads on all 6 and he said he has seen coil packs that tested perfect but started acting up when put in a running vehicle since there are many other different variables when put on a running engine. He asked if I knew anyone with the same model jeep as me... I wish I did. It would cut out a lot of this throwing parts at it crap.

I asked him about catalytic converters and he said no, all the oxygen sensors would be *****ing and there would be a plethora of other problems. Asked about fuel pressure/injection and he pretty much said the same thing as you did Dave... I wouldn't be having a problem with just the one cylinder.

I called Napa while in Dallas and they had a Napa brand and a Mopar for 105 and 120, respectively. Without me asking he goes onto say that both packs are the same. I asked him what he meant and he said "it's just Napa doing their own thing". I asked my uncle about that and he said it wasn't uncommon for store brand parts to use the same manufacturer. I don't know if the guy was full of **** or what but it has a lifetime warranty so I went ahead and got it. If I have any problems I will take it up to the Napa nearby and exchange/pay the difference for name brand.

This one is gray instead of black:



I'm going to put this in tonight so we will see what happens!

 

He's right. There could be a high voltage short that won't show up on a circuit test. That will show you a spark at the tower but blow out under cylinder pressure.

 

Be damned if the misfire wasn't because of the ignition coil rail....

Note that the very first reply on this thread by Cherryokee was to test/suspect the ignition coil rail.

To everyone that had suggestions and contributed to this thread: Thank you. Especially to you Dave1123. I have a new set of boots I bought to put on the old coil rail and the new rail had its own boots and springs. As a very small thank you to you I will mail you the brand new boots if you PM me your mailing address. It is the least I can do for you sticking with me through the whole thread and giving your advice.

Things I have learned:

1) There is no effective way to test the coil rail in these Jeeps. Even if you get a spark on one, that does not mean you will get 6 sparks while the vehicle is running. Keep oil off your boots. I think I might put the old rail back on when I pull the new one off to paint it with the leftover Chrysler orange paint I have leftover (I know I know, I will tape off the entire boots and connector) so I can test all 6 sparks at once. The ohm readings from 1-6, 2-5, and 3-4 were virtually the same on both packs so that isn't a great test. Best thing to do is flag down another jeep like yours when you see one like a crazy person and bribe them somehow to let you switch them to test.

2) Check your compression before you get wrist-deep. I didn't have to do this since I noticed another issue coincidentally while looking into this problem and hastily removed the head.

3) Use a torque wrench when tightening down anything... Especially aluminum. Save yourself a little money from my screw up.

4) Switch the injectors around to see if the misfire follows the injector. Go ahead and get yourself a set of O-rings when you do this.

5) Pull your valve cover off and make sure you have no broken springs or loose rocker arms. Apparently broken springs and stuck lifters are a common problem with this engine.

6) If you have problems after you have overheated, check your casting. It is printed on the driver's side of the block between cylinders 3 and 4. If you have a 0331 head, take your oil cap off and look with a flashlight and see if you have "TUPY" cast into your head. This is the improved 0331 cast that was made in Tupy Mexico that fixes the defective casting. If you don't have a TUPY head, overheated, and getting misfires on 3 and 4, you have probably cracked your head. Get a new one after verifying this from Clearwater. You can find them by googling "Clearwater jeep 4.0 0331 head".

7) Properly change your sparks plugs out with Champions and rule that out. Make sure you are properly gapped at .35 with a gapping feeler gauge. Reapply some dielectric grease when you do and remove/clean your rubber boots carefully to not damage the springs beneath. If your coil rail and boots are covered in grimy oil like mine were, try to get your hands on a coil pack.

8) Check your wire harness around the back of your valve cover. Someone had added some protection and a bunch of tape on mine but it was still sitting on top of the rear driver's side head bolt. I am going to rig something up that zip ties the harness up closer to the firewall.

9) Do not throw money at replacing sensors right off the bat without any error codes that would lead you to believe there is something related going on. Lots of people are buying cam and crank sensors only to find out that they were not causing the problem. Apparently you will have other issues than a single cylinder misfire. For example. The crank sensor fires spark plugs 1-6, 2-5, and 3-4. If there was a problem with the crank sensor causing a misfire, more than likely you would have a P0301 and P0306 code (along with a P0300 code I'm thinking) since these fire at the same time on the coil rail because of some wasted spark design.

10) Learn how to use a multimeter. I already knew how to use one on a real basic level. You can test the ohms on each fuel injector to see if you have any difference, test to make sure you have 12 volts on the GREEN WIRE PIN on each injector with the positive lead on the injector connector and the negative grounded to the frame. You should have a constant 12 volts on each of these. If you don't, suspect a wire harness issue around the back of the valve cover or a problem with the connector.

11) If you can't find any problem with constant voltage to each injector, you can test continuity by googling a PCM connector pinout for your model of Jeep Cherokee and test continuity with your multimeter between the female pin on the corresponding harness connector and other fuel injector connector socket. Any lack of continuity here would lead me to believe you have a wiring problem that should be noticeable if you examine the harness all the way back to the PCM.

12) Check your oil for signs of coolant mixing in. It will smell like antifreeze and be murky dark brown or light brown. Also check your coolant for particles or an oily sheen floating on top. This would indicate a head gasket or issue with cracked head or block.

13) According to my machinist, a well-maintained 4.0 I6 block will stay true. Winterize your vehicles before you have a freeze. You shouldn't need to have your block machined unless you are having piston problems and need to bore out the piston walls. I'm sure I'll have to do this at some point but at least I know what I will be getting into.

Things that may have lead up to this issue:

1) Grimey oil all over my engine. There is a video I have seen online of a woman "adding" engine oil to an engine by taking a quart and randomly and evenly pouring it on top of the valve cover and everything else. I believe that the previous owner did this to my engine. It was unbelievably bad all over.... I would either change the oil myself or take it to the quick lube in town where the guy is really technically competent so it has probably been like that for a while. There was tons on top of the grooves of the valve cover so it would have had to have been a miss when changing oil.

2) I noticed the radiator fan was wired backwards. A little background on this: 3 years ago I was an hour away from home in Wichita Falls and I overheated. I turned on my heater and saw the temperature subside a bit (during the heat of the summer mind you) so I knew I had a bad radiator. I limped it over to a friend's house there in town, got an Auto Zone radiator for like 260 bucks and changed it out. Between the screwed off radiator shroud design and the amount of trouble we had changing out the radiator, I knew I never wanted to do this again. It took like 4 hours and both of us were screaming and cussing. The wires to the fan were short and I added two pair of male/female paddle connectors so I could pull the whole shroud each time without having to cut a wire and redo a bunch of crimp down crap. Fast forward 6 months later and that radiator started leaking. I said **** IT and went to a radiator shop in town to have them change it out. The radiator they had (and the one I currently have) was 140 dollars and hook, line and sinker I got a 280 dollar bill. I drove it for two days and overheated at the drive through at Sonic. I took it BACK to them thinking they knew it was a wire problem and would do the fix on warranty since I had it there two days ago. I ended up getting a 75 dollar bill in the mail. I saw the guy that works for the radiator shop that worked on my Jeep at the bar and I asked him what the problem was and he said "it was a problem with the wiring to the radiator fan".... Well NO **** SHERLOCK. That pissed me off pretty bad and I haven't been to an auto shop since. This was the last time anyone touched that radiator fan or wiring and when he did so the ******* wired it backwards. Obviously this ain't good and I probably got hot several times without noticing or tripping the check gauges notification and caused my head to warp. I'll be fixing the wiring problem tomorrow.

Other thoughts:

The cover that goes over the wiring for the fuel injectors and a couple sensors near the front of the engine... It was broken in half before I got wrist deep into this thing. What the hell is it called? I'll attach a picture from my phone here in a while. I can't find it anywhere online and I would like to replace it.

Is there some high-heat tape that goes around the injector wiring and harness inside of this cover? It seems really brittle and doesn't allow this small gauge stranded wiring to move and jiggle around. I would like to give this entire section a once over since I undid a bunch of it to check the wires.

Finally, I would like to become an active member of this forum to share my limited and un-guided experience with other mechanical newbies. There are tons of people that think they know everything and give bad advice on the internet.... I'm not going to do that. Just share what I have learned by working on my own WJ.

My ABS light has been on and system hasn't been working after reinstalling the head. I'm sure I knocked something loose and if I need help with this I will make a new thread in the appropriate section.

Thanks again everyone and I hope my 1500 or so dollar ordeal helps someone else in the same or similar boat.

 

LMAO!!! Yes, permanent magnet motors like the cooling fan will run in either direction by changing polarity. Another one is the heater blower motor. What I did with mine was put one male connector and one female connector on the fan wires. That way, I couldn't connect it backwards. After reinstalling it, I checked direction by watching cigarette smoke get pulled into the grill.

That piece you want is called the injector wiring loom. AFAIK, there is no insulation in it. When you tie the harness to the firewall, make sure there is enough slack in it to allow for engine movement. Under torque, the engine will try to lift the driver's side, moving the valve cover toward the passenger's side. The opposite in reverse.

All in all, that is a good writeup. When posting on a problem, keep it real. Don't guess and if you do, tell the poster so. This is an "opinion site" meaning what you say is your opinion and should NOT be taken as fact unless verified.

Stay with us. You learned by doing and should pass on your experience to others. BTW, keep your boots, cowboy! LOL!

 

well, I had to chime in here and say good job! you also came back to the thread to let us know the outcome, which is rare. Hey when you checked the resistance of the coil pack did you check the primary resistance? there are 4 plugs and one of the middle ones is the ground. I am currently chasing down misfires and when I checked resistance I measured 1.0 ohms from ground to each terminal. I have an 2001 wj 6 cylinder

 

So from a good ground on the frame to each spring inside the rubber boot you got 1 ohm? Please excuse my ignorance and correct me if I am wrong.

In fact, water down whatever testing you would want me to do and let me know. When I pull my good coil rail to paint the top of it I will do it and post results.