XJ_ND

Hey guys, I've got an '01 Cherokee on my hands and can't get it to pass IL emissions... I'm a new owner, got it with 217k miles and now its not drivable until I clear emissions



Here's the deal:

CODES THROWN:

P0300 (M) Multiple Cylinder Mis-fire Misfire detected in multiple cylinders.
P0305 (M) CYLINDER #5 MISFIRE Misfire detected in cylinder #5.
P0306 (M) CYLINDER #6 MISFIRE Misfire detected in cylinder #6.
P0455 (M) Evap Leak Monitor Large Leak Detected A large leak has been detected in the evaporative system.

The car frequently puts itself into 'limp mode'.


When checking for stored issues on the OBD-II it says the EVAP system is not ready and the O2 sensor is not ready. In my state, you can only have 1 system not ready in order to take the emissions test, and even then there's no guarantee I pass.


Now I've read through a TON of threads with similar issues and people say things like check valves, rotate if needed, change out injectors, coils, fuel rail, replace CPS, temp sensors, O2 sensors, spark plugs, etc. This is quite overwhelming and I'm strapped for cash, so I was hoping someone could impart some wisdom upon me as to where I could start without getting in over my head / over my wallet.


Since it's the '01, I fear it may be the 0331 casted head giving out between 5 + 6, but I don't have the $$$ to take that in to get repaired. Maybe there's a cheap way of replacing the head or patching the gasket myself? Or at least checking to see if that's my issue?



Some more info pulled from OBD-II reader, all taken at idle:

RPM: 816
Coolant: 123.8 F
Load: 9.0%
Intake: 51
Throttle: 16.1%
Vacuum: 14.9in/HG


O2 Sensors: 0.7V, 0.5V, 0.3V, 0.7V

Timing Advance: 2.5 degrees, 36.5 degrees @ 2000RPM



Hoping to take this one step at a time, and fingers crossed it's not the head...

Also, I'm studying electrical engineering, so if there are CAN bus tricks (such as communicating directly with a sensor over the bus, exploring data memory of the ECU and telling it everything is 'OK', or something along those lines, please let me know!)

Thanks guys

Oswalla

For starters here is a bit of info, in the link below, on the Evap system. Your looking for a leak, ideally a smoke test should show where. Look it over for obvious bad hoses or cracked connections, could even be a bad gas cap or fuel tank seal. Probably why shops use smoke pump to detect. Never tried the cigar method, might work good enough.

Misfire 5 & 6, make sure injector wiring is on in the correct order, make sure injector is firing. Take a piece of hose and listen right on the injector, should hear a clicking, or get a noid light. Look at 5&6 spark plugs, are they rusty colored from water. You could rent a cooling system pressure tester and compression tester and do a compression test of 5&6 as well.

http://ka3tfh.com/JeepInfo/XJ/350385...ol-Systems.pdf

Oswalla

Here is a guy that explains what would take me all day to type out. Most of these tests can be done with autozone free rental tools.

XJ_ND

Thank you very much Oswalla! I'll get on with some of these tests and report back. I appreciate you taking the time for that post.

XJ_ND

Ok here's my update:

I pulled the coil rail and the resistance for the coils was in spec. So likely that's not the culprit for now.

Then I pulled the plugs, and they look like this, with 6 on far left and 1 on the right:




yuck, 6th cylinder brownish black, 5th white as a ghost


So that's not good. Five and six are my issues according to the codes, and judging by the plugs the 6th is barely firing or running very, very rich and the 5th is lean as can be. What could cause this?

Went to the store and put new plugs in, Copper+ with correct gap. Not much changed. So I moved on and pulled the fuel rail along with the injectors (after testing and seeing that all of the injectors were in spec for resistance values).

This is what the injectors looked like:




6th on the left, 1st on the right




1 through 5 looked like this... fairly clean




6th injector is a hot mess





Another angle of the 6th




First one bursting at the seams from rust!




Also, fuel rail looks destroyed... rusted as heck


I am about to order new injectors to replace these... I'm thinking Bosch 4-hole ones, unless someone has other recommendations. I'm going to the pick n' pull tomorrow or the next day so maybe I can grab some there, but I'd rather get new ones online unless it's all the same.


So that 6th injector.... what can that tell me about what's happening in the engine? Is this a symptom of a busted head gasket, and should I move on up to checking compression and considering getting the head checked out / rebuilt?


I'd really just like to pass emissions as cheaply as possible, then I can mess with anything afterwards...

Radi

This caught my eye:
If that's the reading after the engine has run a while, you may have a bad coolant temp sensor. That will throw your engine controls a curveball and probably run too rich. Judging from those plugs, you are definitely too rich.

The cracked injector is just that. It doesn't indicate anything other than the injector has failed. I agree with replacing them.

If you had a cracked head or leaking gasket, you'd be losing coolant. Are you?

There is no "limp mode" on an XJ engine. If you are referring to the CEL flashing, that's the misfire indicator. What exactly is happening that you're calling "limp" mode?

XJ_ND

I'll check out the coolant temperature sensor, is that nicknamed TPS around here? Although I thought the coolant was controlled mechanically by a spring that heated and cooled to push around a plate that controlled coolant flow into the engine. I guess you need a sensor for the cluster and PCM though.

I got the thing with barely any coolant in it at all, and haven't seen any noticeable loss but I've also been topping it off after yanking coolant lines to access other parts. I'll keep an eye on that. I did pull the overflow cap at the front and have a friend crank over, only to see plenty of bubbles rush out, if that's any indicator... This thing looks like it definitely overheated a few times, there are even scorch marks at the base of the hood around the back of the engine.

Will do on the injectors.

By 'limp mode': yes, the CEL flashes, but also the RPMs seem limited. If I step on the gas around 25-30 mph, RPM's get to about 3000, and then make a weird shuddering / jerking sequence before shifting into the next gear.

Gonna head to the junkyard now to find a clean fuel rail, coil rail and maybe some injectors to mess with until the new ones come in the mail.

Radi

The TPS is the Throttle Position Sensor, it's attached to the intake venturi.

The thing with the spring is the thermostat. It allows coolant to flow through the radiator when it reaches a certain temperature.

The Coolant Temp Sensor (CTS) is screwed into the thermostat housing. On your year it feeds temp. info to the PCM and to the dashboard gauge.

That's normal if you've been draining and refilling UNTIL the system bleeds itself of air.
If it continues to bubble, you likely have a combustion leak into the cooling system from a head, head gasket or other failure. Most auto parts places have test kits to check for hydrocarbons in the coolant. A positive test means you have a leak.
I'd get this sorted out before doing much else or running the engine much more. It could be the cause of your misfire.
If you have any sign of coolant in the oil, change it. It'll attack the bearings.


RPM will be limited if the engine is misfiring.

XJ_ND

Thanks Radi, that helped clear up my understanding of some things.

So here's a quick update - I think I'm pretty screwed.

I rented a noid light test kit and all injectors are firing. I cleaned the injectors and tossed new o-rings in, swapping 5 and 6 with 2 and 3 to see if one was bad. Doesn't make a difference. Also, pulling the electrical plug on 5 and 6 while the engine is running makes no difference.


Now for the sad news: rented a compression testing kit and read the following after the engine warmed up for ~5 min:

Cylinder 1 - 94
Cylinder 2 - 118
Cylinder 3 - 72
Cylinder 4 - 63
Cylinder 5 - 0
Cylinder 6 - 0


Yep. I think I found the problem.

So now should I pull the valve cover and check out what's wrong? I don't even know where to start, but considering this is an 0331 head with a history of an overheating engine, it seems certain there's a warped / cracked head back there.

Thanks guys... potentially RIP this cherokee since it's been running ~4k miles with this misfire code, so the bearings in the engine could be shot and catalytic converter destroyed. May sell and purchase one with a solid top end.

Thoughts on how to proceed? Maybe try check if I can get the head planed, or check lifters and such?

Radi

If you have good oil pressure the bearings are probably still OK. You can do a basic test of the Cat with a vacuum gauge. (look for youtube videos on finding an exhaust restriction with a vacuum gauge. Basically the vacuum starts too low, doesn't spike after you goose the throttle and often sinks as the engine warms)

You might be able to see something with the valve cover off, but I think you're going to be pulling the head before you're done. Frankly with compression that low I'd worry about the piston rings as well.
How much time and money do you want to sink into it? What about a installing a salvage yard engine?

XJ_ND

I have plenty of time, not much money. Also no garage, all of this is being done outside right now, and not enough equipment to obtain and transport a salvage engine.

I think I'm just gonna open the valve cover tomorrow morning and probably also pull the head. I've read quite a bit about it and I can get that done with current resources. Depending on what I find under the valve cover, I expect to:

- scrape off the head gasket and throw a new one on

- clean the head and potentially get it planed if need be

- remove valve springs w/ compressor tool and lap / seat valves

- check up on lifters since it sounded diesely when it last ran, maybe order new ones

- make sure all push rods are straight

- order a new set of head bolts if there is paint on these ones of course

- change oil

- check for wear on cylinder walls


I have not looked into piston ring replacement, is that something that requires engine removal? I read somewhere that the cam can be removed with the engine and head in place by taking the front end apart so perhaps the rings aren't too bad as well.

Thanks

Radi

Don't forget to check the head and block for flatness with a straightedge and feeler gauge.

At 217K miles it's probably wise to pull the engine and put it on a stand if you're going to do the rings. You'll probably have some cylinder wall refinishing to do, cylinder ridges to remove, crank clean up, bearings, you may find piston skirt issues.... a simple re-ring quite often turns into a whole bottom end rebuild. Not fun bent over the grille with the engine still in the Jeep.

If you still have the compression tester (or can get it), toss a tablespoon of oil in cylinders 1,2,3,4 and see how much the compression comes up. If it's a considerable amount you know the rings are weak.
Hopefully you can identify a failure in the head gasket and some leakage in the valves so you have an easier fix. There are pics here somewhere of where to check the head for cracks.

Was it like this when you bought it? I'd probably defriend the person who sold it to you, it's unlikely they didn't know there were issues. Not that it's any of my business.

XJ_ND

Boy I'd like to rebuild it... don't have the money or space for now though. I have no daily driver, so I'm hoping to get this up to par for now. And don't think I can justify a full rebuild if I can potentially sell this as is for some money and buy a running one for ~$1500 since the current goal is just pass emissions and be road ready. In the near future I'd love to rip apart a 4.0 in an XJ or TJ and build a great machine.

I'll check for flatness for sure though.

Ah yes, I did read about that somewhere... thanks, I'll try that tomorrow morning as well. If it's just the head I'd like to keep this jeep.

I'm young, my dad got it cheap from a stranger as a gift for me. The PO clearly did not treat this XJ well and had almost no coolant in the poor thing when we acquired it. Lost contact with the individual, can't ask any further questions about it's past.

Thanks again. I'll update when I've covered the above.

Radi

That's a particularly bad generation of XJ to run low on coolant and overheat (as you already know). The silver lining in that cloud is that heads aren't too expensive, you can change them yourself with common tools and that may be enough of a fix to get you going.
Awesome of your dad to get you a jeep!

XJ_ND

Cool! And yes, I like the Jeep a lot

Before I took the head off I figured I'd record the engine running to help diagnose things based on the sound... Certainly sounds like a diesel at low RPMs (lifters?) and has a subtle whirring that varies with the revving.



Also, the compression test with oil on 5 and 6 raised both from 0 psi to about 25 psi, if that's any indication of potential piston ring problems.



EDIT:

For those interested and for the sake of documentation:

- I removed the head successfully and found a blown MLS gasket between 5 and 6

- The entire head / top end / intake and exhaust ports are FULL of carbon buildup and crap

- I've solved the misfire (blown gasket, probably warped head but just gonna get a reman'd one)

- For my next steps I have new questions and new goals, and thus started a new thread here:

https://www.cherokeeforum.com/f2/hea...eplace-225520/

Thanks jeepers