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  #1  
Old January 17th, 2017, 16:34
SFXJ125 SFXJ125 is offline
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Rough idle and 3 x codes

Hi all! I'm having a problem with a rough idle on my jeep. It's a 97 with automatic trans. The symptoms are high idle at start-up until it warms up or I throw into gear (which bumps it down to around 1,000). Then after driving for 10-15min, when I slow down to a stop at a light the engine idles very low (like 500rpm) and she shutters a bit. But, it immediately jumps back up to around 700. However, once fully warmed up it idles rough occasionally (~650) and doesn't purrrr like it usually does around ~700-750. It almost sounds like it's misfiring or skipping. The tach drops a tiny bit every time I hear that "misfire".

Tonight I took the jeep to o'reillys and had the associate hook up the scanner. 3 codes came up over and over. P0171, P0133 and P1489. My cursory search on the old interwebs returned near a hundred different suggestions so I figured I'd ask you guys where to start. I don't have the money to just throw new parts at the jeep and would like some suggestions on where to start.

Please be patient as I'm sure I forgot to mention something. Thanks in advance guys!

Edit-P0171 fuel system too lean bank 1
P0133 left upstream o2 sensor
P1489 Aux 5 volt output too low
would a leak in the exhaust system cause all of these codes? I will replace manifold or a portion of the exhaust system if needs be but I dont know how to check for a leak in exhaust and would much rather replace an O2 sensor before replacing major exhaust system parts.

Scotty

Last edited by SFXJ125; January 17th, 2017 at 17:11.
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  #2  
Old January 17th, 2017, 19:56
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Re: Rough idle and 3 x codes

I'd check all your grounds, and battery connections. The 97's were bastard children. I replaced every sensor, the computer, and the fuel pump before Highland automotive diagnosed that the computer was grounding through an oxidized tail light socket on my kid's 97. I added two grounds to the computer connector, and it was happy ever after until the 2nd gear shift solenoid went out. I don't see how an exhaust leak could generate those codes.
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  #3  
Old January 17th, 2017, 20:11
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Kittrell Kittrell is offline
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Re: Rough idle and 3 x codes

A cracked exhaust manifold could easily generate P0171. However, a bad o2 sensor could cause it as well which P0133 could indicate. I would start with the sensor and then move to the manifold if you still have problems. After that, maybe fuel pressure regulator.
P1489 is likely not related to the other two.
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Old January 17th, 2017, 22:57
SFXJ125 SFXJ125 is offline
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Re: Rough idle and 3 x codes

Thanks for the timely response guys. I'll check my grounds as well as the o2 sensor. I just did some wiring for 6 additional driving lights I acquired and maybe I messed something up while working on them. Also, I believe I might be able to elicit the help of my teammate who has a Bluetooth obdii scanner and an android phone app to look at some realtime diagnostics in order to determine if the o2 sensor is bad. I'll get back to you guys with results as soon as I can.

Scotty
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Old January 18th, 2017, 07:31
dan1977p dan1977p is offline
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Re: Rough idle and 3 x codes

If you have a shop vac, you can test for exhaust leaks very easily. On a COLD car, change the vac from suck to blow (sorry had to do the Spaceballs reference) and shove it up the tailpipe. Tape it off to keep it in place and to help it push most of the air toward the header. Listen for hissing to find the obvious leaks. Also feel around from tailpipe all the way to the head for any small leaks. Fix as needed.
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Old January 18th, 2017, 09:59
SolarBell SolarBell is offline
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Re: Rough idle and 3 x codes

From my experience, the first thing I would do is to check the engine block ground straps. I messed one up a while back and it threw all sorts of strange codes.
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Old January 18th, 2017, 11:35
SFXJ125 SFXJ125 is offline
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Re: Rough idle and 3 x codes

Still at work so nothing really new to report yet. During the drive to work this morning the jeep idled low just a couple times during at the stop lights. Again, it's only really happening once the jeep is warmed up and the pattern of occurrence is inconsistent.

Dan1977 ^ I found another forum where someone had described doing this very same thing with pictures and he used a mixture of soapy water sprayed onto the pipes to ID the leaks by bubbles being blown from the vacuum. Thanks for the advice.

On a side note, has any of our CO crew experience with http://www.timbukthree4wd.com/ headers? I was looking through Craigslist last night and found an advertisement for TIG welded stainless exhaust headers for $150 and they looked really nice. Plus, the company is local (Denver area I believe) which always appeals to me, buying American made from local companies.
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Old January 18th, 2017, 11:40
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Re: Rough idle and 3 x codes

Just looks like the typical Ebay headers, stay away.

http://www.timbukthree4wd.com/photo-gallery.php
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Old January 18th, 2017, 21:54
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Re: Rough idle and 3 x codes

Quote:
Originally Posted by Kittrell View Post
Just looks like the typical Ebay headers, stay away.

http://www.timbukthree4wd.com/photo-gallery.php
What would you recommend instead of this one?
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Old January 19th, 2017, 22:56
SFXJ125 SFXJ125 is offline
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Re: Rough idle and 3 x codes

Okay gents, I purchased a new upstream O2 sensor and replaced that along with spark plugs tonight. Upon inspection of the exhaust manifold I discovered a crack just upstream from where the header ends and the down pipe begins. Basically about 2 inches upstream from the connection. I guess it's pretty common for the headers to crack there huh?

So looks like I'll be getting a new header sometime soon. Maybe even a down pipe too cause that thing looks like it took a direct hit with something. It's pinched off to about half its diameter just upstream from the O2 sensor. Is this normal?

I need to figure out how to post pics cause I took some of the crap I blew out the exhaust when I started her up with new plugs and O2 sensor. LOL

Anyways, thanks for the advice guys and we'll see how she drives tomorrow on way to work. I'm in the market for exhaust header so if y'all have recommendations please send my way.
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Old January 20th, 2017, 06:34
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Re: Rough idle and 3 x codes

Quote:
Originally Posted by SFXJ125 View Post
So looks like I'll be getting a new header sometime soon. Maybe even a down pipe too cause that thing looks like it took a direct hit with something. It's pinched off to about half its diameter just upstream from the O2 sensor. Is this normal?
Just sounds like the factory dent for driveshaft clearance on the high pinion axle.





As far as what to put on there as a replacement, really hard to say, Pretty much all of the replacement manifolds out there will crack again eventually. What you can do is get one of the cheap ones and have a new down pipe made with a flex joint in the middle. The flex joint will wear out over time but is much easier/cheaper to replace than a manifold. Or you can spend some coin and get a nice Gibson header, install it and forget about it.
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Old January 20th, 2017, 06:34
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Re: Rough idle and 3 x codes

Quote:
Originally Posted by SFXJ125 View Post
So looks like I'll be getting a new header sometime soon. Maybe even a down pipe too cause that thing looks like it took a direct hit with something. It's pinched off to about half its diameter just upstream from the O2 sensor. Is this normal?
Just sounds like the factory dent for driveshaft clearance on the high pinion axle.





As far as what to put on there as a replacement, really hard to say, Pretty much all of the replacement manifolds out there will crack again eventually. What you can do is get one of the cheap ones and have a new down pipe made with a flex joint in the middle. The flex joint will wear out over time but is much easier/cheaper to replace than a manifold. Or you can spend some coin and get a nice Gibson header, install it and forget about it.
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Old January 20th, 2017, 07:57
SFXJ125 SFXJ125 is offline
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Re: Rough idle and 3 x codes

Kittrell, that's exactly what it is. It seemed almost to "factory" to have been an oops moment for the previous owner.

So far so good driving to work this morning. No rough idles at stops with the tach droping to almost ~500. I will continue to monitor closely and I've ordered a wifi/Bluetooth obdii scanner for my jeep and phone so I can get some real time diagnostics.

I've yet to shove vacuum up the tailpipe and check the whole system for leaks but that'll be either tonight or tomorrow. Will do some more research on a header and get back to y'all. Thanks again!

Scotty
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Old January 21st, 2017, 12:09
SFXJ125 SFXJ125 is offline
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Re: Rough idle and 3 x codes

I was in NAPA yesterday getting some things and I inquired about the cost of a new exhaust manifold. The sales associate started telling me about the 90-92 manifolds on the 4.0l wranglers. He said that they were a better design and made better as far as materials go. Does this sound right? Will that exhaust manifold fit a 97 4.0l with the original intake? It was $167 at NAPA and sounds like a good deal to me. Need to do some more research in it but figured I'd ask y'all as well.
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Old January 21st, 2017, 12:23
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Re: Rough idle and 3 x codes

NAPA is going to have a cheaper version of this. It is a Mopar redesign that incorporates expansion joints to avoid cracking. I honestly forgot about these as no one seems to run them. If you look around you can find them for $105 or so. Probably the best bang for your buck and longevity if you only need a replacement part and are not after performance.

http://www.ebay.com/itm/Jeep-Cheroke...f8U-Zw&vxp=mtr
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