2006 Rubicon Rough Idle

[gbdiaz]

Hey everyone! Recently purchased a 2006 Rubicon 6 speed manual with 81,000 miles on it (Drove it home roughly 1,500 miles and have been driving here at home so it's at about 83K now). Been doing tons of preventative/maintenance on it since I drove it down to it's new home.
To date I've done the following:
1. Changed the spark plugs with Autolite XP985's (Gapped to .035) .
2. Changed the ODPA to the Crown Unit and put back the factory sensor from my original ODPA.
3. Oil and filter changed at the time of changing the OPDA.
4. Changed all 4 O2 Sensors with NTK sensors (referencing the guide for 2005-2006 part numbers).
5. Changed the air filter.

Before changing the O2 sensor, I had a CEL come up and when running my diagnostic tool I got P0157. I cleared it and it didn't pop up until about another week with P0157 again.
I know it's referencing the down stream O2 sensor so I don't think that is what's causing the rough idle. But just to be safe, I changed all 4 O2 sensors.

Now there has been a thread posted before with basically the same symptoms as I have, but their resolution wouldn't be my resolution.
The rough idle is very small, but it's constant. You can feel a little vibration overall and slightly rougher idle every couple seconds.
When driving on the highway, and coming to a stop at a light, some times it will drop as if it wants to shut off, but I give it some revs and it picks back up to normal (although I still have that slight rough idle).
Lastly, like on the other thread, when backing up and stopping, the RPM's drop and almost shuts off. Same as the highway driving, I give it some revs and it picks back up with the slight rough idle. It is a 6 speed.
On my diagnostic tool the RPM's are bouncing between 600-Mid 700's but even with the rough idle, you don't see much movement on the RPM needle on the dash.

I tried Jerry's method of spraying TB cleaner to clean the for quite a bit of time while the engine is idling, but that hasn't cleared up my issue.
I found the original mopar replacement on moparfactoryparts.com but have read in some cases where people swapped it and it still didn't fix the issue. Not sure if it's something I should buy? (I have an 06, so it's the different unit that takes 1 screw under it).

Could it be an issue with the OPDA install? I haven't had a CEL come up, no limp mode, or any other issue since installing it. I did have some trouble installing it, and the OPDA shifted a little. I was sure it would 'cause an issue but the Jeep hasn't had any major issues that you usually see when that is installed wrong (and as mentioned above, I did put back the OEM sensor). Could it be a timing thing anyway?
I believe the rough idle was there before swapping the OPDA anyway. I've read in another thread that it could possibly be the OEM OPDA sensor going bad, which would suck as some say it's not made anymore, and have heard people having issues with ones purchased from NAPA.

Is there anything else I should check in the meantime? The one thing I have not done is check for vacuum leaks, but I'm wondering if that is what would cause my problem? I was planning on doing it this weekend just to be sure as I have the equipment to do it.
I also haven't considered changing the TPS but my issue isn't a high idle.

Let me know if there's any additional info you need from me, but I think I covered everything I've done to this point.
Thank you all for taking the time to read this wall of text.

 

[AWayne]

How did you gap the spark plugs? With a coin gapper? If so, that may be part of it. Platinum and Iridium tipped plugs are very soft material, and can easily be bent or folded.

You may have to just drive for a while and allow the computer to relearn, though.

 

[JKP]

Disconnect the battery to reset the PCM so that it relearns with the new sensors.

The OPDA doesn't adjust the ignition timing. It is for sequentially firing the injectors. If you are not within specs, it will throw a cam/crank sync error code.

05, 06 PCMs are known issues. If it starts shutting down, gauges dropping out while driving, you're going to be replacing the PCM.

Check all the vacuum elbows for cracks.

 

[gbdiaz]

Hey AWayne, thank you for the quick reply! I didn't use the gapping coin, I used that special gapping tool that some members here recommended for the iridium plugs!
Definitely gonna try driving it like you mentioned and see if that clears anything up.

JKP, thank you for the quick response as well. I'll disconnect the battery like you said to reset the PCM and start getting some miles on it to see if it clears up.
In regards to the OPDA, if I'm understanding correctly, you're essentially saying that if I had installed it wrong I would have gotten a CEL by now (It's been driven over at least 50 miles since I installed it)?
Yeah I've read into those PCM issues, so I'm hoping It doesn't get to that point. As of right now, the symptoms you mentioned about a failing PCM aren't things I've had an issue with, so crossing my fingers lol.
Lastly, I just pulled out the smoke leak test machine I have. I need to buy the liquid, so I'll get to that tomorrow. As that's running, I'll give all those vaccum elbows a close look.

 

[JKP]

Yes, once it got up to temp and you got it up above idle, it would throw the cam/crank sensor code and most likely enter limp mode which limits RPM to 2500 or so.

 

[JKP]

Also, you can measure the resistance of the injectors to see if any of them are going out. I forget the resistance of the stock injectors, but they should all measure out to within a few Ohms of each other. If you have any that are substantially different, they are going out.

I think the FSM has the resistance values, you can download it under Resources.

 

[TokenJo]

Wow, for a minute I thought you bought my jeep. Checked the garage and bank account nope jeep is still there and no extra mula in the account . ; ) Welcome to the club. Have done the plugs. 02's (after code, not preventive) no issue. Have not done the OPDA, no screaming monkeys yet. What gas are you running through it? Also do you have cold air intake filter on it? If so, where it crosses the valve cover on the back of the tube that the airflow sensor is plugged in.

 

[gbdiaz]

Wow, for a minute I thought you bought my jeep. Checked the garage and bank account nope jeep is still there and no extra mula in the account . ; ) Welcome to the club. Have done the plugs. 02's (after code, not preventive) no issue. Have not done the OPDA, no screaming monkeys yet. What gas are you running through it? Also do you have cold air intake filter on it? If so, where it crosses the valve cover on the back of the tube that the airflow sensor is plugged in.

Lol! Are you having a similar issue? Just running 87 in it and it still has the stock intake/box I just replaced the filter.

 

[gbdiaz]

Also, you can measure the resistance of the injectors to see if any of them are going out. I forget the resistance of the stock injectors, but they should all measure out to within a few Ohms of each other. If you have any that are substantially different, they are going out.

I think the FSM has the resistance values, you can download it under Resources.

Gonna give this a shot as well, thank you!

 

[Jerry Bransford]

87 octane is all that's needed so you're good there.

When I had a misfire and bad idle on my 04 TJ when I bought it used, replacing the cats fixed it, one of the pre-catalytic converters was fooling the PCM and causing intermittent misfires, bad idles, and Check Engine lights. The previous owner said he had the same intermittent problems and had already replaced the O2 sensors. The same O2 sensors were reinstalled with the new catalytic converters 10-11 years ago and no problems since.

What triggered the replacements of the cats was one of the pre-cats came apart internally and its innards blew downstream into the man cat plugging it up. I was on the highway at the time and my top speed dropped to about 5 mph within a quarter mile or so.

 

[gbdiaz]

87 octane is all that's needed so you're good there.

When I had a misfire and bad idle on my 04 TJ when I bought it used, replacing the cats fixed it, one of the pre-catalytic converters was fooling the PCM and causing intermittent misfires, bad idles, and Check Engine lights. The previous owner said he had the same intermittent problems and had already replaced the O2 sensors. The same O2 sensors were reinstalled with the new catalytic converters 10-11 years ago and no problems since.

What triggered the replacements of the cats was one of the pre-cats came apart internally and its innards blew downstream into the man cat plugging it up. I was on the highway at the time and my top speed dropped to about 5 mph within a quarter mile or so.

Hey Jerry, thank you for your response! Do you think maybe the early stages of bad cats would cause that minor rough idle with no other symptoms? I just looked past cats initially because I have no loss of power (or at least it doesn't feel like it), and MPG has been on par with what others are getting. But now that you mentioned it, it has me thinking that although it may not be at the point that it bogs the motor down, it could be at the early stages of doing so. My TJ did come from the rustbelt so the most weathered part is the exhaust. I was doing some homework on exhausts yesterday and I am liking the look of the flowmaster unit (Just the double cat unit). I'd opt to just remove that third cat altogether if I needed to go that route.

Side note, I just wanted to thank you for your wealth of knowledge and willingness to share here on this forum. I grew up around Jeeps 'cause of my father, and I am fortunately in a position to own a beautiful example of one. Since purchasing it, this forum has been such an amazing resource for me. Almost every thread I have come across, I have seen your name and Chris' pop up with sound advice so I appreciate your dedication and contribution!