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Old 07-22-2011
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P0171, better mpg?

The vehicle is a '96 Ranger, 4 cyl, 5 speed, 2WD

I recently got a check engine light which Autozone told me is a "P0171 System too lean bank 1". I haven't confirmed this yet, but I seem to be getting better fuel mileage... I'm at around 340 miles with 1/8 tank to go, I usually get to 320 or so as I'm rolling into the gas station on E.

Has anyone ever heard of this happening? I understand there's a good chance my fuel gauge is coincidentally on the fritz, and I'm about to run out of gas... any thoughts?

Thanks!
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Old 07-22-2011
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I dont know alot about this, but it seems to make sense that if its running too lean, that it would not be consuming as much fuel, too rich and then you would be consuming more fuel.
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Old 07-22-2011
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MAF dirty is all I can think of. Search that code and it'll tell you what needs to be done
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Old 07-23-2011
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thanks for the tip. sounds like a good place to start anyway
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Old 07-23-2011
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why are there two threads about this?
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  #6  
Old 07-27-2011
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UUGGGGhhhh...

I have been battling this p0171 for 2 weeks now.

Replaced so far: MAF Sensor, EGR, DPFE Sensor, IAC Valve, and replaced the entire gasket set for the upper area (valve cover, intake manifold, throttle body) PCV and a new Fuel Filter as well.

Oh yeah, and plugs and wires.....and air filter, and checked fuel pressure, its good too....

My gas mileage has decreased, Running too lean does mean less fuel, BUT, when it detects a lean mixture, it calls for more fuel in the system

Good luck with it man....its a doosey...

Also, first order of business would be a vacuum leak....that will throw a p0171
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Old 08-01-2011
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I found a decent sized hole in the cat, don't know if that could let extra air onto an 02 sensor and throw a lean code. It's scheduled at the exhaust shop on friday so we'll see.
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Old 08-08-2011
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new cat.... check
check-engine light still on.... check

I'm going to clean the MAF sensor, replace the PCV valve, and then maybe block off the EGR valve if the problem persists. If none of that works, I may have to start spening some money...
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Old 08-16-2011
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cleaned the MAF sensor, replaced the PCV valve, and blocked off the EGR valve... still got a P0171 lean code.
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Old 08-16-2011
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vacuum leak or bad DPFE sensor. Thats my guess. DPFE can cause a lean condition by keeping the egr open longer than it should. I think its like 50 bucks to replace.

http://shop.advanceautoparts.com/web...1160898911____
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Old 08-16-2011
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Is there any way to verify the dpfe sensor is bad, voltage or resistance specs I could check with a multimeter?
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Old 08-16-2011
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Old 08-16-2011
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Just thinking outloud here but have you checked the O2 sensor?
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Old 08-16-2011
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Thanks for the link. I haven't checked the O2 sensor yet. Despite the fact that the P0171 code references the O2 sensor ahead of the cat, I was under the impression that the O2 sensor was more likely to be detecting the problem than causing it. Maybe it's time to add the O2 sensor to the list of possible culprits... you wouldn't happen to know specs to check on that would you?
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Old 08-16-2011
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I dont know the procedure for the o2 but if its faulty i could see it giving false readings.
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Old 08-19-2011
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You said your CEL is still on, but have to reset the ECU by disconnecting the neg (-) terminal for a short while and seeing if the code is thrown again?
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Old 08-31-2011
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the problem is finally solved... back in post #9, where I claimed that I still had the P0171, I was wrong. I still had a CEL, but I was just assuming it was still P0171. On a whim, I went and had the code read again and what do you know, it was a new one. I forget the exact code, but it was something to do with the EGR valve. so it turns out that when I cleaned my MAF sensor I fixed the problem, and then simultaneously created a new one by blocking off the EGR valve. I unblocked the EGR valve (which was probably a stupid thing to do in the first place) and the CEL is gone!! lesson learned, try one thing at a time.
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  #18  
Old 08-31-2011
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Quote:
Originally Posted by 94mtx View Post
You said your CEL is still on, but have to reset the ECU by disconnecting the neg (-) terminal for a short while and seeing if the code is thrown again?
yeah, I would disconnect the battery after each attempt at fixing the problem and it would come back at around 8-10 miles of driving. Currently I'm over 100 with no light so I think I finally got it.
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Old 10-05-2011
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Quote:
Originally Posted by teddyb View Post
The vehicle is a '96 Ranger, 4 cyl, 5 speed, 2WD

I recently got a check engine light which Autozone told me is a "P0171 System too lean bank 1". I haven't confirmed this yet, but I seem to be getting better fuel mileage... I'm at around 340 miles with 1/8 tank to go, I usually get to 320 or so as I'm rolling into the gas station on E.

Has anyone ever heard of this happening? I understand there's a good chance my fuel gauge is coincidentally on the fritz, and I'm about to run out of gas... any thoughts?

Thanks!
Well mostly this means the engine is burning the standard amount of gasoline/air mixture. Which means you might be getting better mileage, but have terrible power or acceleration, and could be damaging the engine. I would check all air intake sensors, and then check other fuel related sensors, most likely a MAF sensor because if this goes on the fritz, then it will read incorrect air flow readings and burn improperly
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  #20  
Old 10-06-2011
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I had a CEL in my '06, bank 2, downstream, stuck lean, I cleared the code and it hasn't come back on yet and this was abt 2 months ago. I got 66k miles
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