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Unread 08-06-2010, 09:22 PM   #1
millerbd
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1997 TJ Wrangler 
 
Join Date: Aug 2009
Location: Bremen
Posts: 3
codes p0171 and p0172...too rich and too lean?

Hey everyone, I have a huge problem that Ive been trying to diagnose throughout the ownership of my TJ, about a month or so. It runs like crap and guzzles gas like crazy! Its a 97 with a 2.5.

Here are the symptoms....the codes it has thrown are p0171 and p0172, running too rich and running too lean. about a week ago it would idle very low, around 500 or so, but has since become normal. It has absolutely no power....I mean aside from being a 2.5 anyways, it feels like I am constantly driving uphill and against a strong wind...its hard to even get it up to 60mph. Also, sometimes it drives fine and has power throughout the RPMs, other times its terrible and both low and high RPMs. The only time I feel any power is a WOT.

Here are what I have tried to do to fix the problem: Both o2 sensors have been replaced, spark plugs replaced, air filter, throttle body and IAC cleaned, cleaned fuel system with GUMOUT and lucas fuel treatment (not at the same time). Here are some things I have suspected: TPS, MAP sensor, fuel injector, fuel filter, fuel pump, intake manifold gasket, EGR valve, sensor connections....who knows.

So if anyone else has run into this problem or know of someone who has....Id appreciate any help. Otherwise I have to set the jeep on fire.

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Unread 08-07-2010, 06:02 AM   #2
millerbd
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bump

no one can help?
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Unread 12-13-2010, 11:54 AM   #3
rroadkilll
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1997 TJ Wrangler 
 
Join Date: May 2007
Location: Hertford NC
Posts: 247
Did you set it on Fire???
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I can't wait to tear it up in the mall parking lot with you some day Jay... we could park on each other's tires all flexed out taking up 4 parking spots, walk in the mall with our jeep keys dangling for everyone to see, hit up some abercrombie and fitch, then go back outside and hang out by the jeeps for a few hours... maybe get risky and drive over some curbs.. :highfive:
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Unread 12-13-2010, 02:18 PM   #4
1982cj8
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2005 LJ Wrangler 
 
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Posts: 625
First check the fuel pressure and volume, then check the catalytic convertor to see if it is beginning to plug up. Normaly when fuel system lean or rich codes come up it is fuel or plugged exhaust, you already did some of the basics.
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Unread 12-13-2010, 02:28 PM   #5
Ross
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2001 TJ Wrangler 
 
Join Date: Dec 2002
Location: BUM****, MO
Posts: 10,402
Quote:
Originally Posted by millerbd View Post
Hey everyone, I have a huge problem that Ive been trying to diagnose throughout the ownership of my TJ, about a month or so. It runs like crap and guzzles gas like crazy! Its a 97 with a 2.5.

Here are the symptoms....the codes it has thrown are p0171 and p0172, running too rich and running too lean. about a week ago it would idle very low, around 500 or so, but has since become normal. It has absolutely no power....I mean aside from being a 2.5 anyways, it feels like I am constantly driving uphill and against a strong wind...its hard to even get it up to 60mph. Also, sometimes it drives fine and has power throughout the RPMs, other times its terrible and both low and high RPMs. The only time I feel any power is a WOT.

Here are what I have tried to do to fix the problem: Both o2 sensors have been replaced, spark plugs replaced, air filter, throttle body and IAC cleaned, cleaned fuel system with GUMOUT and lucas fuel treatment (not at the same time). Here are some things I have suspected: TPS, MAP sensor, fuel injector, fuel filter, fuel pump, intake manifold gasket, EGR valve, sensor connections....who knows.

So if anyone else has run into this problem or know of someone who has....Id appreciate any help. Otherwise I have to set the jeep on fire.
My Chevy Cobalt (yes I have a Jeep) is throwing a 0171 which is also running lean. My exhaust started getting loud and it started rattling about the same time. For me I suspect the cat.

My 01 TJ started losing power, It is not a DD so I don't much attention to gas mileage. I changed the cat and it got better. The muffler fell of and it got even better, I suspect pieces of the Cat were clogging the muffler. The Jeep never threw any codes.
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Unread 12-13-2010, 03:24 PM   #6
millerbd
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1997 TJ Wrangler 
 
Join Date: Aug 2009
Location: Bremen
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Well, since the post I think I figured it out. It has a small leak from the exhaust manifold, actually there is a bolt missing. So I think that some fresh air is getting into the exhaust, messing with the oxygen sensors, reading high level of oxygen in the system. I probably won't get around to changing the gasket or checking the manifold so my quick fix is unplugging both oxygen sensors.....and now it runs great! and I get on average 17mpg. The only problem now is it runs a little rough when cold, just for a couple minutes though.
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Unread 12-14-2010, 07:17 AM   #7
Ross
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2001 TJ Wrangler 
 
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Location: BUM****, MO
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Quote:
Originally Posted by millerbd View Post
Well, since the post I think I figured it out. It has a small leak from the exhaust manifold, actually there is a bolt missing. So I think that some fresh air is getting into the exhaust, messing with the oxygen sensors, reading high level of oxygen in the system. I probably won't get around to changing the gasket or checking the manifold so my quick fix is unplugging both oxygen sensors.....and now it runs great! and I get on average 17mpg. The only problem now is it runs a little rough when cold, just for a couple minutes though.
I was just talking to a friend of mine at work. He has a couple race cars and builds engines (hobby not professional). He was saying that if you run to lean you can damage parts in the motor. With my car running lean I have picked up a couple mpg.
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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Unread 12-14-2010, 08:09 AM   #8
LJinNOLA
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2004 LJ Wrangler 
 
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Location: New Orleans, Louisiana
Posts: 102
Had that (just 0171) on my toyota and it was the intake gasket leaking. Looks like you're good now. There are lots of possible causes for too lean or too rich.
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Unread 12-16-2010, 09:17 AM   #9
Ross
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Mine ended up being a leak in my exhaust. My car has a part of the exhaust that has a flexible section. That is where the leak is.
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Schitzangiggles: We used to teach our children to fight evil, now we teach them that fighting is evil.

2001 TJ, 33 trxus MTs , W, locked, belly up, some armor.

"If you aim at nothing, you will hit it every time." Zig Ziglar
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Unread 06-10-2012, 12:08 AM   #10
AndyKraft84
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1997 TJ Wrangler 
 
Join Date: Jun 2012
Location: Chesapeake, VA
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Hello "1997 TJ Wrangler" ...I just got the same codes on my 97 Jeep Wrangler 2.5. How is yours doing now? How did you find that exhaust leak? Thanks
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Unread 04-04-2013, 06:32 AM   #11
Tylervalo
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2003 TJ Wrangler 
 
Join Date: Sep 2010
Location: Strawberry Plains
Posts: 30
I hate to bump and old thread, but have the EXACT same problem ('97 4cyl, too rich and too lean and drinking gas). Anyone ever figure out the solution?
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code , error , p0171 , p0172 , tj , wrangler

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