Runs like a champ, idles like crap

[DUB]

Following this thread, as I sometimes have funny idle and everything (almost) is new in terms of wear and tear parts / sensors. But I have never changed my upper cats. Though, I do have a new one I purchased 5 years ago, never installed. So Im ready when the time comes.

My idle is always low and vibrates the rig, slight stumble off idle. Not convinced it is the cats as I have zero loss of power up high, at least that I am aware of. Feeling like it is an 02 sensor wire or plug as of now.

Not hard to remove the pipe and inspect the cats, provided all the hardware isn't seized...

 

[AndyG]

Following this thread, as I sometimes have funny idle and everything (almost) is new in terms of wear and tear parts / sensors. But I have never changed my upper cats. Though, I do have a new one I purchased 5 years ago, never installed. So Im ready when the time comes.

Good for you- it is inevitable.

 

[Davidryan123]

This may sound a bit simple but I had a rough idle when I purchased my jeep a few months ago. The previous owner just putted around in it and really kept it under a few hundred mile a year. So, a few weeks ago I drove it on the highway ~70mph for about 1.5 hours non-stop. The rough idle is all but gone, there is a slight tremble every once in a while but it's got 125k on it.

 

[fourpointzero]

This may sound a bit simple but I had a rough idle when I purchased my jeep a few months ago. The previous owner just putted around in it and really kept it under a few hundred mile a year. So, a few weeks ago I drove it on the highway ~70mph for about 1.5 hours non-stop. The rough idle is all but gone, there is a slight tremble every once in a while but it's got 125k on it.

I'll tell you what, that absolutely was the case for me as I do garage my Jeep every winter. And in fact, it seems to be a reoccurring thing each season. Now, with fresh gas in the tank my symptoms are basically what you describe- a little rough idle now and again. Maybe I'm expecting some type of perfection that doesn't exist for the TJ's. But I have to also consider that Im still working with what Im guessing are the OG top cats (back cat was replaced 5 years ago) and I haven't changed my plugs in 12 year when I was @135k, currently sitting at 195k.

 

[DUB]

Funny you say that. When I drive it for a long trip on the freeway (hour or so) it does get better for a short while but then comes back. This is what has me thinking it is a bad 02, like it's running rich at idle when not WFO for a while...?

Seriously, this has been bugging the heck out of me!

 

[astjp2]

Spark plug resistance can cause idle roughness.

 

[DUB]

Spark plug resistance can cause idle roughness.

I have tried Champions and since switched to Autolite XP-985, no change for me..

 

[fourpointzero]

I have tried Champions and since switched to Autolite XP-985, no change for me..

I was going to go with Autolite APP985. I guess there's multiple applications for the TJ.

 

[Davidryan123]

I'll tell you what, that absolutely was the case for me as I do garage my Jeep every winter. And in fact, it seems to be a reoccurring thing each season. Now, with fresh gas in the tank my symptoms are basically what you describe- a little rough idle now and again. Maybe I'm expecting some type of perfection that doesn't exist for the TJ's. But I have to also consider that Im still working with what Im guessing are the OG top cats (back cat was replaced 5 years ago) and I haven't changed my plugs in 12 year when I was @135k, currently sitting at 195k.

Yep. I've replaced all (4) sensors on my exhaust since I had one that threw an alarm. I do feel sometimes it's a problem "breathing" intake or exhaust, but it's not a everyday driver and IMO the juice isn't worth the squeeze for now.

 

[DUB]

Could use some help from a guru here on these readings, trying to interpret through searching now.

Engine at full temp on idle.

 

[macleanflood]

Can it graph those voltages?

Grossly and completely oversimplified they're under .9v and operating correctly...at the exact moment in time you took the picture...

-Mac

 

[DUB]

Can it graph those voltages?

Grossly and completely oversimplified they're under .9v and operating correctly...at the exact moment in time you took the picture...

-Mac

I believe yes, I can graph them. I am looking for consistent up and down swings correct? Are the negatives concerning?

 

[macleanflood]

I believe yes, I can graph them. I am looking for consistent up and down swings correct? Are the negatives concerning?

My knowledge of O2s is crude, unsophisticated and limited. All I know is that you want the voltages to trend below .9v.

Someone with more knowledge then me would have to answer that one.

-Mac

 

[Vtx531]

Sometimes people will go about changing out a bunch of sensors trying to fix a problem. If you buy cheap ones on ebay, amazon, autozone, etc, you will be chasing your tail forever because now you created a bunch more problems. Not sure if that is the situation here but for anyone reading- you really need to stick to only oem parts or high quality original supplier brand parts these days. Especially for sensors or electronics.

 

[macleanflood]

You really need to stick to only oem parts or high quality original supplier brand parts these days.

Agreed but...if Mopar is available it's sourced from China. Standard Motor Products and Echlin are ones we've had luck with.

Amazon and eBay are rife with counterfeit products too.

Whatever you do don't throw out the originals.

-Mac

 

[DUB]

Parts I have used to try and fix this problem have been OEM accept for maybe the coolant sensor and map, however nothing changed during the process. Going to get after this again today and see what I can find, if anything. I may just be living with it..

King of a bummer when I drove my kids 06 and my buddies 04 and they idle normally and feel a bit more peppy.

 

[DUB]

Pulled the 02's and ran it, no difference, think the cats are fine. At this point guessing valve train is just getting tired at 160k now.

S&J engines is only a 4 hour drive for me considering a new 4.0 or maybe 4.7 in the future. I don't see rebuilding the head being worth it.

 

[fourpointzero]

Pulled the 02's and ran it, no difference, think the cats are fine. At this point guessing valve train is just getting tired at 160k now.

S&J engines is only a 4 hour drive for me considering a new 4.0 or maybe 4.7 in the future. I don't see rebuilding the head being worth it.

Whatever you decide to do, please keep us posted. Can be a great resource for other members. Wish you the best. Cheers

 

[DUB]

Whatever you decide to do, please keep us posted. Can be a great resource for other members. Wish you the best. Cheers

Absolutely! I have learned a ton from here and would like to help out when I can!

 

[The (LJ) Dude]

S

Absolutely! I have learned a ton from here and would like to help out when I can!

So...how did you make out?