Continued Engine Issues. Help!

[QuinnD]

Hello, I posted here about 6 months ago about starting to mod my 2000 Jeep Cherokee XJ for overlanding, however, there have been persistent engine issues. Currently, the most troubling one is a consistent but random misfire on cylinders 1 and 3. Battery connection has been checked and fixed, spark plugs have been replaced, ignition coil replaced, and compression test has been performed, all good there. A potentially unrelated thing: radiator has been flushed, new coolant was added. I've read across the internet that it could be the IAC or O2 sensor which I am unsure of how to check those things. The odd thing is is that it doesn't throw codes very often when the check engine light goes off, even when the check engine light is blinking. Not sure where to go from here, slowly going insane lol.
Edit: These misfiring issues also cause my heat gauge to go out, only happens with these misfires and usually starts working mid-drive.
Edit 2: I do not have a distributer cap I have an electronic ignition

 

[Viking1204]

I assume when you replaced the spark plugs you made sure the gap was appropriate for your particular engine?

 

[socal66]

Could be somewhere in the electronics. I had the exact same issue with a 2000 Dakota truck (which is a totally different engine and platform) and it was a bad throttle position sensor which I replaced and then everything was good after that.

 

[QuinnD]

I assume when you replaced the spark plugs you made sure the gap was appropriate for your particular engine?

I’m pretty sure, it was done by a mechanic a few years ago.

 

[Offroadnutz]

Read about a similar problem on another 2000 on cherokeeforums.com
They ended up replacing the distributer that the cam sensor sits on . Something about the wear in the gear causing excessive movement. ``
If that is the problem, you would need a scan tool synchronize the cam and crank sensors after replacement.

 

[Viking1204]

I’m pretty sure, it was done by a mechanic a few years ago.

On my old 2011 F-150 it would start misfiring every few years and resplacing the spark plugs would fix it.

 

[QuinnD]

I’m pretty sure, it was done by a mechanic a few years ago.

On my old 2011 F-150 it would start misfiring every few years and resplacing the spark plugs would fix it.

Hmm okay I’ll look into that

 

[MidOH]

Cap, rotor, plugs. Remove and clean ground wires.

 

[Alanymarce]

Try replacing the wiring from the distributor cap to the plugs. You may have done this already, and I guess the distributor may have come with new wiring in which case ignore this.

 

[QuinnD]

Try replacing the wiring from the distributor cap to the plugs. You may have done this already, and I guess the distributor may have come with new wiring in which case ignore this.

I haven’t looked into that yet, someone else mentioned checking the cap too, thanks!

 

[Alanymarce]

I haven’t looked into that yet, someone else mentioned checking the cap too, thanks!

I misread the posts and thought that you'd already replaced the cap, so yes - cap AND wiring.

 

[QuinnD]

I haven’t looked into that yet, someone else mentioned checking the cap too, thanks!

I misread the posts and thought that you'd already replaced the cap, so yes - cap AND wiring.

Just discovered I don’t have a distributer cap, I have an electronic ignition (I’m still learning) so I guess it’s definitely electrical

 

[Alanymarce]

Just discovered I don’t have a distributer cap, I have an electronic ignition (I’m still learning) so I guess it’s definitely electrical

hmm - so, check the wiring from the coil to each plug, I suggest.

 

[Jonathon]

I am assuming you have the 4.0 inline 6 that Jeep put in most of their vehicles. I would start by checking all of you spark plug wires. (Check for rubbing, burnt sections, or even crimped and cuts.) From there replace the coil packs if you haven't. If this hasn't solved the issue I would start following all of the wires around the exhaust manifold. I had a wire loom there on my jeep that had come disconnected from a bracket that had fallen on the manifold and burnt a hole through the loom and some of the wires. (depending on year the side of the engine bay can change this.) After that I would take and ohms meter and test the O2 sensors. On the Jeep I would put in Mopar o2 sensors. (after market ones work but don't tend to last from my experience.) The o2 sensors will be located on the exhaust. (see image) I would also check the fuse panel for any blown fuses. (there are more than fuse panel. I dont' know where they all are on your xj.) Most of the fuse panels on jeeps I have worked will have one in the engine bay, another in the glove box (idk if this is also on xjs or not) and sometimes near the drivers side under the left side of the steering wheel. From there I would start checking sensors. Hope this helps. If you have any questions Ill try and answer them.

 

[QuinnD]

I am assuming you have the 4.0 inline 6 that Jeep put in most of their vehicles. I would start by checking all of you spark plug wires. (Check for rubbing, burnt sections, or even crimped and cuts.) From there replace the coil packs if you haven't. If this hasn't solved the issue I would start following all of the wires around the exhaust manifold. I had a wire loom there on my jeep that had come disconnected from a bracket that had fallen on the manifold and burnt a hole through the loom and some of the wires. (depending on year the side of the engine bay can change this.) After that I would take and ohms meter and test the O2 sensors. On the Jeep I would put in Mopar o2 sensors. (after market ones work but don't tend to last from my experience.) The o2 sensors will be located on the exhaust. (see image) I would also check the fuse panel for any blown fuses. (there are more than fuse panel. I dont' know where they all are on your xj.) Most of the fuse panels on jeeps I have worked will have one in the engine bay, another in the glove box (idk if this is also on xjs or not) and sometimes near the drivers side under the left side of the steering wheel. From there I would start checking sensors. Hope this helps. If you have any questions Ill try and answer them.

Hey, thank you for your response. I recently figured out the issues, it was the cyl 2/5 fuel injectors/sparkplugs, the head gasket, and the thermostat sensor/housing. However, and maybe you know better than me, my cyl 2 is still misfiring (sometimes it throws a code sometimes it doesn’t) and it throws even though it runs smooth, starts up smooth, and has a smooth idle. Someone mentioned heat soak, I’m worried it’s carbon build up. But it’s ONLY cyl 2.

 

[Jonathon]

I am assuming you have the 4.0 inline 6 that Jeep put in most of their vehicles. I would start by checking all of you spark plug wires. (Check for rubbing, burnt sections, or even crimped and cuts.) From there replace the coil packs if you haven't. If this hasn't solved the issue I would start following all of the wires around the exhaust manifold. I had a wire loom there on my jeep that had come disconnected from a bracket that had fallen on the manifold and burnt a hole through the loom and some of the wires. (depending on year the side of the engine bay can change this.) After that I would take and ohms meter and test the O2 sensors. On the Jeep I would put in Mopar o2 sensors. (after market ones work but don't tend to last from my experience.) The o2 sensors will be located on the exhaust. (see image) I would also check the fuse panel for any blown fuses. (there are more than fuse panel. I dont' know where they all are on your xj.) Most of the fuse panels on jeeps I have worked will have one in the engine bay, another in the glove box (idk if this is also on xjs or not) and sometimes near the drivers side under the left side of the steering wheel. From there I would start checking sensors. Hope this helps. If you have any questions Ill try and answer them.

Hey, thank you for your response. I recently figured out the issues, it was the cyl 2/5 fuel injectors/sparkplugs, the head gasket, and the thermostat sensor/housing. However, and maybe you know better than me, my cyl 2 is still misfiring (sometimes it throws a code sometimes it doesn’t) and it throws even though it runs smooth, starts up smooth, and has a smooth idle. Someone mentioned heat soak, I’m worried it’s carbon build up. But it’s ONLY cyl 2.

I would check sensors if it is running smoothly. Idle ahould be between like 750 and 950. Think of the inline 6 as a tractor engine running on gas (in short what it is but thats off topic.) I use a obd2 reader connected to my phone to verify. The app i believe was 10 dollars and is called car scanner. Most wifi or bluetooth obd2 readers should be able to woth the right app give you accurate enough gauges yo verify idle, air temp, or even look up temps. Could be a leak on a vacuum line as well. Thats where I would look next. If engine goes vroom but light says bad. Check sensors and vacuum lines next.

 

[Jonathon]

I am assuming you have the 4.0 inline 6 that Jeep put in most of their vehicles. I would start by checking all of you spark plug wires. (Check for rubbing, burnt sections, or even crimped and cuts.) From there replace the coil packs if you haven't. If this hasn't solved the issue I would start following all of the wires around the exhaust manifold. I had a wire loom there on my jeep that had come disconnected from a bracket that had fallen on the manifold and burnt a hole through the loom and some of the wires. (depending on year the side of the engine bay can change this.) After that I would take and ohms meter and test the O2 sensors. On the Jeep I would put in Mopar o2 sensors. (after market ones work but don't tend to last from my experience.) The o2 sensors will be located on the exhaust. (see image) I would also check the fuse panel for any blown fuses. (there are more than fuse panel. I dont' know where they all are on your xj.) Most of the fuse panels on jeeps I have worked will have one in the engine bay, another in the glove box (idk if this is also on xjs or not) and sometimes near the drivers side under the left side of the steering wheel. From there I would start checking sensors. Hope this helps. If you have any questions Ill try and answer them.

Hey, thank you for your response. I recently figured out the issues, it was the cyl 2/5 fuel injectors/sparkplugs, the head gasket, and the thermostat sensor/housing. However, and maybe you know better than me, my cyl 2 is still misfiring (sometimes it throws a code sometimes it doesn’t) and it throws even though it runs smooth, starts up smooth, and has a smooth idle. Someone mentioned heat soak, I’m worried it’s carbon build up. But it’s ONLY cyl 2.

Also try running it foe a few minutes. Then shut it off and pull number 2 cylindar apark plug and check cap and conidition of apark plug. It shouldnt have oil or anything like that on it.

 

[Terrax]

Zht