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I am looking for some help. I have a 99 TJ Sport 4.0 Automatic Straight 6. Headers in lieu of catalytic converter and Air Fram system, otherwise she is stock. The Jeep was parked for about 3-4 weeks while I was away, and when I came back and started her she ran fine for about 15-20 mins then the check engine light came on and it felt like the motor wanted to jump out of the hood. It felt like she was choking, sputtering, sluggish and had lost power. I was quite a distance from home by then, but close to an Auto Zone so I stopped in and talked with a guy there explaining what was going on. He suggested the fuel injectors being clogged and to try a bottle of Lucas Fuel Injector Cleaner. He said I had the proper amount of gas in her so all I had to do was pour in the cleaner.

I drove her home with no change. My husband hooked her up to his hand held computer the code indicated was p0171 Lean Bank 1. I told him I put the Lucas in and he suggested calling the dealer and seeking their advice, as the Jeep book didn’t cover this topic.

The dealer indicated that this code is common and unfortunately can cover a wide variety of fixes/parts. He told me that if we were at all capable to start with a full and complete tune up and oil change. He told me search for a vacuum leak. He said with labor at $60/hr and $90 diagnostic charge they would also begin with the tune up and didn’t want to charge me if I could do it myself.

I also started Google searching the code and realized quickly the differences for all other vehicle approaches to this code and the Jeep approach. I bought platinum plugs, top of the line wires, cap, rotor, Penzoil (the only oil that has ever been used in her) and new filter, I cleaned the Air Fram Filter with air filter cleaner. We checked all over the top and the bottom of the motor for a hose or vacuum leak and found none.

Many forums noted the Map Sensor as the culprit so we bought a new one and installed it too. My husband shut the code off and we took her for a test ride and she ran great, I mean absolutely fantastic, I was so happy for about 20mins. We shut her off and were right back where we started, the motor was sputtering, lost power, she just ran awful. We shut the code off three times and each time she ran great then **** the bed.

Many forums addressed the O2 sensors, while others within the same threads discredited this advice immediately saying they never blow. Many forums address the fuel to air ratio giving specific ratio numbers. I have no idea how to figure this out? Is this only something the dealer can determine? There is no way that I believe that the fuel filter or pump is the culprit, because when we shut the code off she runs great, no problems, if it was either of those parts there is no way that she would run that good for 20 mins or until I shut her off, then like I said, she starts sputtering.

I really think that would be a sensor issue as the computer reads the sensor and notes a problem the light pops on and the motor runs terrible. O2 sensors are $70 each and needing 2 that might not be the problem seems a waste of money. The Map sensor I replaced was $60, the oil and tune up ran me about $125 and it did nothing.

Please help me if you have encountered this code and found the answer I would really appreciate any advice that you may have with a solution. I miss my baby so much as I am not driving her for fear that something else may break as she really is running terribly.
 

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Sounds like a rough one... I had the same exact prob with my 89 wrangler... It would run 15 to 20 mins and start to act crazy... Spit, sputter , and sometimes shut off... etc... I did not have a code reader so I was completely lost.... I to started replacing parts... Plugs and wires, fuel filter, premium gas and injector cleaner, distributer coil, tune up ...etc.... Now I said that to say this, nothing can be ruled out until its thoroughly checked and even then it could still be the problem... I thought the same about the fuel pump and tank, that's there's no way it could be the problem or it would do it act crazy from the moment it cranked up... 500 dollars later and a few wasted hours changing parts I spent 50 bucks on a fuel pressure gauge kit to check my fuel pressure inline while the truck was running down the road... Come to find out I had great pressure but after 15-20 mins of run time ( no matter what speed) it was overheating and the safety shut off on the pump was cutting it off and on repeatedly... I could stop for 5-10 mins crank it back up and go again for the same amount of time.... I would advise some light trouble shooting before replacing anything else... Fuel,Spark, and Combustions... Can't do with out either..I hope this helps.... If you can get it in the yard while its spitting and sputtering you can get your husband to spray starting fluid in the breather towards the motor and if the motor catches up your running out if gas... It could be a lot of thing and I'm no mechanic... Just my experience with mine...


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