kustomlarry

2000 Cherokee sport that I have owned for 12 years. I have put over 250k on it. I absolutely love this car and I am looking for a little guidance. I have a few issues that all may be related. I have searched on here and the most helpful posts I found are so old the pictures are gone.

Last summer it started having an issue with a misfire. It wasn't all the time but I could drive the car without a problem from a to b. If I stopped anywhere along the way and restarted the motor would idle improperly and i would get a flashing engine light. Eventually I had to replace the crank sensor after it decided to stop running a few times and everything was good. Now it seems to have started again. If I drive the car for a bit, and it varies, I can shut the car off and turn on and the misfire goes away. I would love to be able to stop if I have to after work and not worry about this.

The electric fan does not seem to be coming on at all and the temperature seems to fluctuate between from the lower quarter to midline on the gauge. I have checked the fuses and nothing is blown. I am not sure but this can't be helping the situation if the misfire.

I love driving this thing and with 310k + on it it deserves to be taking care of.

Thanks in advance. I have always found a ton of information on this site. I work mostly on older cars, etc.

BlueRidgeMark

If you bought an aftermarket CPS, it could be the CPS again. They have a really, really bad track record. NTK/NGK are the only brand you should use. This is the factory brand. NAPA carries them, among others.

But pull some codes and let us know what you find. Troubleshooting is much easier with codes! Many auto parts stores will pull the codes for you, for free.


It's probably best to start a separate thread for a separate problem. That said, fan not coming on could be the temp sensor. But first, verify that the fan itself is good. You'll find a connector over on the side where the fan is located. Follow the lead coming from the fan. Disconnect it, and use some jumper wires to provide 12v straight from the battery. Don't worry about polarity. If you get it wrong, it will spin backwards. No harm done. You just need to see if the fan works at all. If it doesn't, replace it. If it does, we start more troubleshooting.

kustomlarry

I do not remember what brand I put in the car. I read how they had issues with non-oem pieces.

There are two codes:

P0304. - cyl 4 misfire
P0204. - fuel injector 4 circuit/open.

My question is can this happen only after it is hot?

Thanks

BlueRidgeMark

Sure!

Heat can open marginal connections, make parts seize, and otherwise mess with your mind.

Might be a heat-soak issue. It's a known problem with the later Cherokees. I think it's a 2000-2001 thing, mostly. Do a search here and you'll find plenty of info on it.

And yes, it can start as a car ages, where it's never been a problem before.

kustomlarry

Thank you. I have read many articles on early Pontiacs and their heat spikes. I will do a search today.

The codes shot may very well be a heat issue I suppose. At least it is a start.

4WD4EVER

X2 on the recommendations by BRM.

You may not necessarily have a heat-soak issue though (though it certainly is a possibility). It could be a chaffed wire to the #4 injector or the #4 injector itself. I would inspect the wire harness. Particularly where it comes across the left, rear part of the cyl. head. There is a stud that is known to rub through the harness there. Also, try switching the #4 injector w/ another, clear the codes and see if the code follows the injector or not. I wouldn't throw money at a heat-soak kit (or anything else just yet).

Edit: To be clear: Since the codes thrown are for the #4 injector circuit, you want to isolate that injector ( and related components. e.g. the connector, pins in the connector, etc.).

By swapping out the injector with, say, the #5 injector, if it is indeed the #4 injector itself, it will then throw the related code (p0205 & p0305). Make sense?

kustomlarry

Sent direct power to the fan. No luck so ordered a new fan today. Baby steps.

extrashaky

Sounds like multiple things going on here. Start with what you know:

Have you pulled your spark plugs? What does #4 look like?

Here is how I would proceed if it were mine:

The circuit code sounds like you may have a wiring issue with #4. Borrow a noid light kit from Auto Zone or a similar parts store. Get the motor hot so that it starts misfiring, then plug the noid light into the #4 connector and see if it's getting the signal to squirt. I suggest this first because you don't have to take the fuel rail off to do this. NOTE that the noid light may cause you to get another fuel injector code (because the wire is connected to the light instead of the injector), so don't be surprised by the new code.

If the light is flashing normally, look closely at the #4 injector to see if it's cracked. If you can't see anything wrong with it, pull the fuel rail off and try swapping your #4 injector with one further away from it, perhaps #1, to see if the problem follows the injector. If #1 then starts misfiring, you know you have a bad injector.

If you have one bad one, go ahead and replace them all while you're in there. You might even consider upgrading to four hole injectors.

If neither of those tests find your culprit, my next step would be to test the compression in your cylinders to see if you have a head issue causing your #4 misfire. A #4 misfire can be a symptom of a cracked 0331 head. Don't assume the worst, but it's a good idea to do this (free) test to rule it out before going too much deeper into the weeds.

A fuel-related misfire can also be caused by a broken valve spring, so my next step would be to pull the valve cover off and inspect the springs and rockers. I recently had this happen to mine. It doesn't sound like yours is acting like mine was, but unfortunately not all misfires act the same.

After that, I got nothin' and would have to start looking for other ideas.

That part definitely sounds like heat soak, except that it's usually #3 that has the problem. Read this:

https://www.cherokeeforum.com/f2/hea...6/#post3328474

Now, can you have heat soak AND an injector problem? Yes you can. And if you have an injector problem can heat soak make it worse? Yes it can. A cracked or leaking injector in particular can be affected by heat soak, because it has a place for the fuel to evaporate out.

Come to think of it, another free test you can do is to check your fuel pressure. See if you're getting the correct pressure (49 psi + or - a few lbs) and whether that pressure is leaking down when you shut the motor off.

Are you sure your electric fan isn't working?

Here's where the 2000 and 2001 XJs are weird. Starting in 2000, the electric fan does NOT come on automatically when you turn on the A/C, and it does NOT come on at 217° like in prior years. It only comes on when the A/C high side pressure reaches 280 to 320 psi and goes off when the line pressure drops to 235 psi, OR it comes on when the coolant temperature reaches 223° F and goes off when the temp drops to 217°. Normal operating temp in these things is 210° to 220°, and the middle line on the gauge is 210°. If you're never going above that middle line, you're not getting it hot enough to kick on the electric fan.

So again, are you sure your electric fan isn't working?

extrashaky

Sorry, didn't read all the way down. Still, keep in mind how the fan works on a 2000 and don't be surprised when the new one doesn't come on. I seriously doubt the fan is the source of your misfire issue.

BlueRidgeMark

Yeah, I think you nailed that one.

kustomlarry

I agree it isn't part of the misfire issue but I want to address it.

kustomlarry

Fan installed last night and found multiple cracked injectors. After 310k I think it is time to change them.

BlueRidgeMark

Daaaa, ya think?

Let us know how it runs!

4WD4EVER

If you're undecided about who/where you're going to purchase injectors from I'd recommend contacting username jhc7399. He sells them and he has a solid reputation and very reasonable prices. Here's a link to him:

https://www.cherokeeforum.com/f72/78...ectors-222140/


Here's a write-ups to assist with the swap if you're not familiar or comfortable with the process. As BRM stated, let us know how it goes.


https://www.google.com/amp/s/thexjgu...ctor-swap/amp/

kustomlarry

Emailed him for a set. In the meantime I will change the radiator cap and t-stat.