2006 Jeep Wrangler fuel/ignition problem

[Don70]

I have a 2006 Wrangler and have been experiencing some stalling issue when decelerating. A few days ago the check engine light came on. I checked the diagnostic codes and codes said a mis-fire on cylinder 2 and bad O2 sensor at catalytic converter. The converter was also getting hot and the engine started missing really bad. I found an issue with the spark plug cable on cylinder 2 and have replaced all 4 cables and all 4 plugs. The plugs that I removed were light brown to white in color with some darker discoloration on the plug from cylinder 2. I checked the diagnostic codes again and the mis-fire code was no longer present. The O2 sensor was still present. I replaced the O2 sensor and the missing improved...meaning not near as bad and the engine feels like it has a bit more power now but the catalytic converter is still getting hot and the miss is still present. At the tailpipe it sounds like a puffing noise and there is a slight smell of gas if you put your hand in front of the tailpipe. Any ideas?

 

[Chris]

First and foremost, what brand of O2 sensor replacement did you use?

 

[Don70]

First and foremost, what brand of O2 sensor replacement did you use?

Bosch was the only one they had. I also ran a bottle of fuel system cleaner with a full tank of gas and it appears that some progress has been made. I was thinking that a fuel injector was sticking or possibly leaking. Figured I would try it before possibly working at that. Still hesitating when accelerating and exhaust sounds like its popping. As for the catalytic converter I just let it run for about 30 minutes and took it around the block and it appears to not be getting hot where it is glowing. Ideas?

 

[Jerry Bransford]

As has been said in this forum countless times, Bosch is a brand of O2 sensor that does not work well in our Jeeps. The only brands that are known to work properly and consistently are NTK and NGK which is what the factory installed, those brands are one and the same. No guarantees of a fix but I'd replace that Bosch.

I am however confused by where you said the cat does not appear to be getting hot where it is glowing.

 

[Chris]

Two things:

1) Bosch O2 sensors (as Jerry said) are notoriously and very well documented as having issues with our TJs. The only brand you should be using is NTK / NGK. I really can't rule your O2 sensor out of the issue do the the large number of issues with the Bosch O2 sensors and how they don't perform correctly in TJs. I would sincerely consider swapping it out for an NTK / NGK.

2) I am also confused where you say, "it appears to not be getting hot where it is glowing". Well, that's good, because it shouldn't be glowing, that would be bad! If by chance that is a typo and you meant that it IS glowing, well then that is definitely not good.

The reason for the cat glowing is that something is causing raw unburned fuel to be sent down the exhaust pipe where the cat "burns" this fuel. The cat is designed to burn the tiny amount of unburned fuel that comes from a normal engine. Now, if you pour excessive hydrocarbons (fuel) in the exhaust, the cat will burn that too and since it's burning too much fuel it glows red hot. This won't last very long, this is very damaging to the cat. The catalyst can get hot enough to melt. And that won't take long! And when it melts, then you will have a blob of molten metal blocking the exhaust pipe (now it's clogged!) and the engine will stop operating. At that point, the only fix is replacement of the catalytic converter.

However, if you find and fix the problem now you can avoid that expense. You have to find why raw fuel is going through the engine. The most common reason would be a bad spark plug or bad spark plug wire. If the spark doesn't work, there is no "combustion" in that cylinder and the raw unburned fuel goes out the exhaust pipe.

I have a suspicion that the culprit here could actually be the Bosch O2 sensor. I'm not exaggerating when I say that they are very well documented as having lots of issues on the TJ, right out of the box.

 

[Don70]

Two things:

1) Bosch O2 sensors (as Jerry said) are notoriously and very well documented as having issues with our TJs. The only brand you should be using is NTK / NGK. I really can't rule your O2 sensor out of the issue do the the large number of issues with the Bosch O2 sensors and how they don't perform correctly in TJs. I would sincerely consider swapping it out for an NTK / NGK.

2) I am also confused where you say, "it appears to not be getting hot where it is glowing". Well, that's good, because it shouldn't be glowing, that would be bad! If by chance that is a typo and you meant that it IS glowing, well then that is definitely not good.

The reason for the cat glowing is that something is causing raw unburned fuel to be sent down the exhaust pipe where the cat "burns" this fuel. The cat is designed to burn the tiny amount of unburned fuel that comes from a normal engine. Now, if you pour excessive hydrocarbons (fuel) in the exhaust, the cat will burn that too and since it's burning too much fuel it glows red hot. This won't last very long, this is very damaging to the cat. The catalyst can get hot enough to melt. And that won't take long! And when it melts, then you will have a blob of molten metal blocking the exhaust pipe (now it's clogged!) and the engine will stop operating. At that point, the only fix is replacement of the catalytic converter.

However, if you find and fix the problem now you can avoid that expense. You have to find why raw fuel is going through the engine. The most common reason would be a bad spark plug or bad spark plug wire. If the spark doesn't work, there is no "combustion" in that cylinder and the raw unburned fuel goes out the exhaust pipe.

I have a suspicion that the culprit here could actually be the Bosch O2 sensor. I'm not exaggerating when I say that they are very well documented as having lots of issues on the TJ, right out of the box.

Thanks for the responses....just to be clear the glowing catalytic converter I was referring to occurred about 3 days ago. That evening I went to Oreily's and ran codes. Codes came back as mis-fire on cyl. 2 and the O2 sensor at converter slow to respond. I then found a bad spark plug cable and replaced all 4 as well as the plugs. After that the misfire was gone and the catalytic converter was still getting excessively hot...I didn't check temperature but was glowing orange in the day time. We ran codes again and came back with only the O2 sensor.....and I just remembered a code for the thermostat. Sorry for leaving that one off the first post. I then purchased the only O2 sensor they had...which was Bosch. I just read another post in a forum and saw where someone posted that they had to replace the thermostat as well so I was about to try that....I will also attempt to replace the Bosch O2 sensor with a NTK. I was just stating that the catalytic converter doesn't appear to be getting as hot as in glowing since the work above has been completed. My main concern now is the rough idle/stalling and rough acceleration...which has improved but is still not correct. I am going to read codes again and then replace the O2 sensor with an NTK type and replace the thermostat as well and let everyone know the status. If you can think of anything else that an average person like me could verify please post. Thanks again for the help!

 

[Chris]

Well, if you get the chance, replace the Bosch O2 sensor with an NTK / NGK one. I know it seems odd, but the issue with Bosch O2 sensors is a very big one, and it's very well documented as well. I suggest swapping it out, because honest to god, that could be your issue.

If you have a code for the thermostat, definitely replace that as well. Do those two things and I'm betting your issue resolves itself.

 

[Don70]

Well, if you get the chance, replace the Bosch O2 sensor with an NTK / NGK one. I know it seems odd, but the issue with Bosch O2 sensors is a very big one, and it's very well documented as well. I suggest swapping it out, because honest to god, that could be your issue.

If you have a code for the thermostat, definitely replace that as well. Do those two things and I'm betting your issue resolves itself.

I had the codes rechecked. This time the code was the MAS/MAF sensor dirty, O2 secondary running rich (or something like that) and the thermostat (don't recall what the error said). I just replaced the Bosch O2 sensor with an NTK brand. Cleaned the MAS/MAF sensor. Started the jeep and basically the same thing. I disconnected the battery for about 10 seconds to see if that will reset the codes. Didn't let it run long due to wanting to change the thermostat. By the way, is the thermostat located where the radiator hose attaches to the block? Thanks again for the responses.

 

[Don70]

I had the codes rechecked. This time the code was the MAS/MAF sensor dirty, O2 secondary running rich (or something like that) and the thermostat (don't recall what the error said). I just replaced the Bosch O2 sensor with an NTK brand. Cleaned the MAS/MAF sensor. Started the jeep and basically the same thing. I disconnected the battery for about 10 seconds to see if that will reset the codes. Didn't let it run long due to wanting to change the thermostat. By the way, is the thermostat located where the radiator hose attaches to the block? Thanks again for the responses.

Never mind I found it. I will update after replacing.

 

[Chris]

Okay, staying tuned for the update!

 

[Don70]

Okay, staying tuned for the update!

Just replaced the thermostat. No change with the miss/rough idle and acceleration.
So as of right now the following has occurred:
- replaced spark plug cables (this cleared the mis-fire code)
- replaced spark plugs (plugs that were removed appeared to be ok though)
- change out secondary O2 sensor Bosch
- changed out secondary O2 sensor to NTK
- cleaned MAS/MAF sensor or whaterever you call it (it was dirty)
- changed thermostat

Just test drove the Jeep for about 12 miles. Curretly there is not CEL on however the jeep still has a miss. The miss appears to be more profound under 2K RPM. Thoughts?

 

[Don70]

Just replaced the thermostat. No change with the miss/rough idle and acceleration.
So as of right now the following has occurred:
- replaced spark plug cables (this cleared the mis-fire code)
- replaced spark plugs (plugs that were removed appeared to be ok though)
- change out secondary O2 sensor Bosch
- changed out secondary O2 sensor to NTK
- cleaned MAS/MAF sensor or whaterever you call it (it was dirty)
- changed thermostat

Just test drove the Jeep for about 12 miles. Curretly there is not CEL on however the jeep still has a miss. The miss appears to be more profound under 2K RPM. Thoughts?

Just had codes read again after the CEL light came back on. Cylinder 2 mis-fire is back, and the secondary O2 sensor too rich is still there. I assume the O2 code is due to the mis-fire. Any idea on how to check the coil pack? Whats the probability of it being an injector or cylinder? Jeep has 132K miles on it.

 

[Chris]

Highly unlikely it's the cylinder, and injectors don't usually go bad either.

It could indeed be a coil pack, I wouldn't rule that out.

Here's one way to test them (a brilliant way if you ask me):

And another:

Test the coil pack if you can and see if it's working. That will at least rule it out.

 

[Jerry Bransford]

Try disconnecting the battery's negative lead for 3-5 minutes to reset the computer. 12 miles may not have been enough for the computer to catch up with the new NTK O2 sensor.

 

[Chris]

Try disconnecting the battery's negative lead for 3-5 minutes to reset the computer. 12 miles may not have been enough for the computer to catch up with the new NTK O2 sensor.

X2. Didn't think about that, but there's truth to it!

 

[Don70]

After disconnecting the battery for about 10 minutes and then driving the jeep around a bit further. I returned to Advance Auto....the misfire code P0302 on cyl. 2 had returned. Along with the secondary O2 sensor. Changing the thermostat fixed the fault code for it. I think you were correct it took driving the jeep around a bit longer because after I found the faulty spark plug cable this fault had gone away. As for the O2 code I believe it is being displayed due to the mis-fire condition on cyl. 2 which is also creating the miss/puffing exhaust.

 

[Chris]

Well, you're almost all the way there!

Have you tested the coil pack to be sure? That's the next thing I would do!

 

[Don70]

Well, you're almost all the way there!

Have you tested the coil pack to be sure? That's the next thing I would do!

Coil pack was tested by using one of the old spark plug cables and a spark plug. I disconnected the plug cable at the coil pack for cylinder #2. I then connected a previously removed spark plug into a previously removed spark plug cable. I connected my "test" cable to the #2 position on the coil pack. I then grounded the "test" spark plug threads to the negative terminal on the battery using one lead from a set of jumper cables. I started the engine and observed the electrode on the "test" spark plug and found that no arc was present. I turned the jeep off and disconnected the "test" plug and cable and reconnected the coil pack to the plug on cylinder #2. I then disconnected the spark plug cable from the coil pack for cylinder #1 and connected my "test" spark plug cable and spark plug using the same method above and found that an arc was present after the engine was restarted. I also noticed that the engine was running a bit rougher due to possibly having only 2 cylinders firing. I then tested the coil pack for cylinder 2 once again. I wanted to verify that there was no arc present. Once I confirmed that there was not an arc present, I felt like the coil pack for cylinder #2 was bad. I then verified that the coil pack operates 2 cylinders at a time by reading more information on this site. Due to being fired in pairs and only having a mis-fire (P0302) on cylinder #2 , I pretty much confirmed that the coil pack was bad.

I replaced the coil pack and the problem was solved! Thanks to both of you for the advice and information. I spent $168 versus what the mechanic shop quoted me which was between $300 - $1000. Thanks again and Merry Christmas!

 

[Chris]

That's friggin' fantastic! I had a sneaky suspiscion it was the coil pack. I've seen a lot of misfire issues lately, and every single time it's been a bad coil pack.

Anyways, glad you got it figured out and saved a lot of money in the process. Merry Christmas!