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Discussion Starter #1
My car has this hesitation stutter while in first gear between 1k and 2.5k rpm. The acceleration sucks as well. My CEL came on and I hook a diagnostic machine up to my ECM and the code read bank 1 sensor 1 too lean. So I changed my a/f upstream o2 sensor, and then got my ECM reset and my CEL went off for a little, after three days it came back on so I disconnected my negative battery wire and reconnected it to turn the light off then with a few hours it was back on. I hooked the machine up again and the same read out came up I know the o2 sensor is installed correctly so I don't know what the hell it could be. There is an abundant sense of gas odor coming from my engine as well as a lag between me pressing the throttle and engine response. I just want suggestions on what is causing this **** because I can't figure out nothing.
 

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Hi!

Please don't engage the swear filter -- though I certainly understand you're upset!

From the description bank 1 too lean I am assuming your code is actually CEL P0171. Is this correct?

Follow this but be very careful with the MAF. In my experience cleaning the MAF usually solves the problem if -- repeat, if -- the intake is the correct part and sealed right, the filter is the correct part and new, there is no aftermarket BOV and no other intake leaks (in this case a BOV is an intake leak effectively...). Check everywhere/anywhere for a leak while you are at it (it's good sport) and don't forget to at least glance at the line to the fuel pressure regulator - but my money is on a MAF if the car is stock, or the part not stock if the car is not stock.

P0171 CEL Thread - Everything you ever wanted to know? - NASIOC

more:
http://www.clubwrx.net/forums/general-maintenance-troubleshooting-accidents/134311616-mass-air-flow-sensor.html

more still:
http://www.clubwrx.net/forums/general-maintenance-troubleshooting-accidents/134301944-p0171-problem.html?highlight=p0171

and in general:
ClubWRX Forum - Subaru Impreza WRX and STi Community and Forums - Search Results
 

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Discussion Starter #3
Where is it located?

Aight so clean the MAF got it that should help out. But regarding the fuel pressure regulator where is that located, as well as the line that leads to it? And have both an aftermarket k&n filter and a hks BOV both fit correctly and the filter is sealed. So I guess I will clean the MAF and see what that does. Would you recommend me cleaning my fuel injectors as well. Would that make a difference
 

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Focus on the FPR lines near the passenger side bottom by the rails. Your injectors have to be really fouled to generate the CEL IMO. See quotes from link below. Some aftermarket filters can foul the MAF.

4. Fuel pressure regulator. According to the factory service manual and suby techs, the most common problem with the FPR is the vacuum connection to the intake manifold (either cracks in the hose where it makes a sharp bend, or a leaking connection.)
Occasionally, the fuel pressure regulator reference line will pop off or is accidentally left off when working on or around items located near the passenger side fuel rail. (ie. injectors, spark plugs, reaching for something...) This is a serious mess up, but one that is easily corrected.

5. Check all ground connections. While you can certainly verifiy all of them, one person mentioned specifically being able to fix their problem by checking their grounds. They discovered that the ground wire on the drivers side of the intake manifold (the bolt) was loose and was causing the P0171. Make sure that bolt, and all others, for that matter are tight. This one is somewhat random, but it's so easy to check.

6. Injector problems. I came across two people who posted about a P0171 after removing AFTERMARKET injectors and going back to stock injectors. In both cases, the stock injectors had been sitting in a box inside their houses for over a year. It was believed that the fuel had crystalized and caused a blockage of some sort on one or more of the injectors. This could potentially happen with ANY used injector that has sat for a long time. In both cases, the individuals used fuel system cleaner (is it called "heet"?) and the P0171 went away.


 
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