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Discussion Starter · #1 ·
First time jeep owner long time admirer. Bought 97 Tj 2.5 148K miles July 2011 from friends of family for DD. Got it cheap enough so no worries right? Needed some TLC. PO replaced fuel pump, plug wires and cap. As I was going home after purchasing check engine light came on code was P0171. Checked code and figured because of the age and miles on it probably needed the cat replaced. Replaced cat and code cleared for a day. Replaced O2 sensr day after replacing cat. Code went away and has been gone until now.
Same code just started popping up. Just recently replaced TStat (the one in it was stuck open keeping it from maintaing 195 degree temp for ECM fuel mixtures) and muffler. Night before changing Tstat disconnected Neg Bat Terminal to cleanse ECM. Ran great day of changing Tstat and this morning on the way to work popped back up. Feels like it is chugging which is what it felt like last time O2 needed changed. What are the odds I could have another clogged O2 sensor? Is it possible to clean them or not worth the trouble? I have not replaced the TPS but am leaning towards this to as it is one more thing I havent done. Please advise. :rolleyes:
 

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P0171 is a lean condition in bank 1. Basically the O2 sensor is seeing too much oxygen in the exhaust right out of the engine before the catalytic converter. I would check for a crack in the exhaust manifold or a bad exhaust gasket. I have also heard using Bosch O2 sensors causes problems too. Your replacing a whole bunch of parts you probably don't need to replace. Also check for a vacuum leak somewhere.
 

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I kind of figured as much thanks. I did use a Bosch 15705 for a replacement. There is a small exhaust leak at the manifold somewhere. Muffler shop couldnt see it and it is not real noticeable. Didnt think it was big enough to cause this big of an issue. So if it is the sensor can you clean those things our or are they used up when they start throwing codes? Thanks for the help.
 

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No, just because it is throwing a code doesn't nesscearily mean the sensor is bad. It means the sensor "sensed" something is wrong and set a trouble code. Now it could be a bad sensor but when you told me you have an exhaust leak that tells me it is most likely doing its job. In all actuality O2 sensors should never go bad for the duration that most people own their vehicles for. I've heard people say you need to change them every so often, but what I learned in college while training to be a mechanic is that they should never wear out with normal wear and tear. With that being said I have read that a lot of people have problems with Bosch O2 sensors on their Jeeps. Fix the exhaust leak before replacing the sensor is what I would do.
 

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I'm curious if you replaced exhaust manifold and if it fixed the issue? I took mine to a mechanic after I got the P171 code and started having similar issues as u described. I replaced wires, plugs, cap and rotor. Also cleaned throttle body and added fuel treatment and 93 gas. Reset the engine light and all was fine for a day or 2 then light reappeared. I started looking at engine and noticed the bottom bolts to exhaust manifold are not there and looks as if there's a gap between block and manifold. Took it to mechanic and quoted $600 saying exhaust manifold needs resurfaced and the bottom bolts were broken off. He did a smoke test and doesn't appear to have any cracks. I'm thinking of replacing the manifold myself since I've found a Dorman for $80. But how does he know if it needs to be resurfaced if not removed? Should I just replace? I've found helpful threads to do the job. But the resurface idea has me 2nd guessing it all.
 

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I have a 97 Jeep wrangler I purchased a year ago cheap from a guy who told me the transmission had gone out turned out to be the clutch had burned out. well did a tune up only cause check eng light was on and the code was po171 replaced spark plugs, wires, cap, rotor, distributor position coil nothing. found small exhaust leak at the manifold replaced with new oxygen sensor front and rear ran good for a few days then code came back, replaced manifold temp sensor and Map sensor and tie wrapped all the existing vacuum lines attached to the manifold. Still code comes out gas mileage still about 140mi. a tank gets a little better after each replacement of parts but gradually goes back to bad gas milage. Is there any way of pinpointing where to look next ??? I've read ignition coil, fuel pump, injectors, fuel regulator, Throttle position sensor, coolant sensor. there has to be way to fine the problem any suggestions.
 

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I have a 99 jeep tj 2.5l. Same issues. Replaced map sensor checked all vaccum lines. Had intake resurfaced new intake gasket. New o2 sensors. New IAT sensor new plugs engine rebuilt 10,000 miles ago. All new internals. Catalytic converter not plugged no exhaust or intake leaks p0171. Bank 1 too lean. Shrtft 32.8% not sure what else to throw at her. I have a scan tool and can give more numbers. Oh and by the way fuel pressure at the rail running 46 psi. Please help. Just empty every pocket right?? Some one has had to have this issue.
 

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I have a 99 jeep tj 2.5l. Same issues. Replaced map sensor checked all vaccum lines. Had intake resurfaced new intake gasket. New o2 sensors. New IAT sensor new plugs engine rebuilt 10,000 miles ago. All new internals. Catalytic converter not plugged no exhaust or intake leaks p0171. Bank 1 too lean. Shrtft 32.8% not sure what else to throw at her. I have a scan tool and can give more numbers. Oh and by the way fuel pressure at the rail running 46 psi. Please help. Just empty every pocket right?? Some one has had to have this issue.
Sorry I can't help with your question but I thought I'd post to welcome you to the forum and bump your post to the top of the forum. Hopefully someone with some experience with this issue will chime in soon.
 

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I have a 99 jeep tj 2.5l. Same issues. Replaced map sensor checked all vaccum lines. Had intake resurfaced new intake gasket. New o2 sensors. New IAT sensor new plugs engine rebuilt 10,000 miles ago. All new internals. Catalytic converter not plugged no exhaust or intake leaks p0171. Bank 1 too lean. Shrtft 32.8% not sure what else to throw at her. I have a scan tool and can give more numbers. Oh and by the way fuel pressure at the rail running 46 psi. Please help. Just empty every pocket right?? Some one has had to have this issue.
Did you ever find the issue
 
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