HELP!! Cherokee fuel problem?? P0171

cjgolfer7

Well-Known Member
Joined
Apr 17, 2010
Location
SC
I have a 1997 Cherokee 4.0 aw4 231. It all started a couple weeks ago when I had to jump my jeep off. It took unusually longer for it to fire. I got in to and pumped the pedal to get it to catch and it fired right up and it's never been the same. Started idling rough and drinkingggg gas. I mean like 5 mpg. A couple days go by and I bought new plugs, wires, cab, rotor, fluids to do a routine tune up and it throws the check engine light on the way to advanced. Scanned it there and code P0171 bank 1 running lean. I'm no master mechanic but this thing was spitting out black crap and gas from the tail pipe. All I smell is fuel but no leaks. Changed all that stuff throw some sea foam in and still same crap. Changes the oxygen sensor close to the header, Upper I believe. No black junk but will still spit a lot of fuel out and running rough. Idk what else to do or the problem. I cleared the code and filled it up to head out of town tomorrow so we'll see how it does. But only a matter of miles before the code gets thrown again. When I return I plan on replacing the other oxygen sensor but after that is not sure. Any and all help and ideas and thoughts would be greatly greatly appreciated. Thanks in advanced.

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Why did you change the oxygen sensor?
First things first watching the o2 sensors determine if they are fixed lean. If they are introduce a touch of propane into the brake booster hose while watching the o2 sensors, . If it switches rich you know the sensor is functioning and you truly have a problem indicating a lean condition. However as youve described it sounds like a rich condition. Map sensor, fuel pressure, a injector or a leaking fuel pressure regulator could all be the cause of a rich condition. Also could have an exhaust leak before the o2 You also should take a look at fuel trims an d see what their doing. If in fact it thinks its lean when its not it will obviously be extremely rich.
You could also have a pcm fault or a wiring fault but regardless of what it is you'll have to start with some live data. It is a speed density engine so vacuum leaks typically cause a high idle.
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I had read somewhere that faulting oxygen sensors could lead to it and my upper was shot. I thought the same thing seems like it's a rich problem. The idle hasn't changed except for a little sputter. Like a slight skip. When the fuel comes out the tail pipe it comes in waves.. you start it up nothing for like 5 mins, then the next five mins I feel guilty for not collecting the fuel that's coming out and reusing it.

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cjgolfer7 said:
I had read somewhere that faulting oxygen sensors could lead to it and my upper was shot. I thought the same thing seems like it's a rich problem. The idle hasn't changed except for a little sputter. Like a slight skip. When the fuel comes out the tail pipe it comes in waves.. you start it up nothing for like 5 mins, then the next five mins I feel guilty for not collecting the fuel that's coming out and reusing it.

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Lol understand that. Oxygen sensors can lead to it, but its a very simple test to determine if they are operating prior to replacement.
Theres a bunch of shop owners on here. Where are you located? I'm sure theres someone close who can help.


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I'm in atl now, but come up to western nc and upstate sc a good bit. I drives fine for now just like to do a little better than 6 mpg hah.

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cjgolfer7 said:
I'm in atl now, but come up to western nc and upstate sc a good bit. I drives fine for now just like to do a little better than 6 mpg hah.

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I'm in blowing rock if your up this way give me a shout and I'll help out if I can. Theres a very good shop in savannah named intergrity auto repair if you get that direction at all.

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Sounds good thanks for your help. Interesting enough I filled it up and put 250 miles on it and have in between a half and quarter tank. But still kinda runs a little rough at idle. But hasn't thrown a code or seem like it's drinking gas.

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