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Old 22 Jan 2008, 09:01 pm
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Default How to fix '97 Accord CEL P0170 & P0171 Codes?

My Accord has 190K miles. Any suggestions on how to fix codes P0170 (Fuel trim bank 1) and P0171 (System too lean)? I'd hate to start playing the sensor replacement guessing game. I've seen some posts indicating it could be the upper O2 and others say it's a vacuum leak. Where should I start and what should I check after that? Thanks.
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Old 22 Jan 2008, 09:31 pm
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Replace the O2 sensor.
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Old 22 Jan 2008, 09:46 pm
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Your primary O2 sensor is responsible for adjusting your A/f ratio, and if it is faulty all sorts of problems will result, including a lean running condition. Replace the primary O2 sensor quickly, as a lean running condition could cause detonation, leading to very costly repairs.It COULD be a vacuum leak, but that is a very slim possibility. Go ahead and check all vacuum lines while your under there changing out that oxygen sensor just to be sure.
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Old 22 Jan 2008, 10:01 pm
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The P0171 is caused by a lean condition that the PCM can no longer adjust for. The condition is caused by the deterioration of a fuel metering component or system that has occured over time. Over time the PCM has been making adjustments to fuel trim to compensate for the deterioration of the fuel metering system until now when the need to adjust (compensate) has exceeded the PCM's ability to do so.the cause could be a deteriorated O2 sensor but that will usually cause a code P0136 for the O2 sensor range or response fault. More likely it is a mechanical problem such as low fuel pressure, a restricted fuel filter or a worn fuel pump. Misadjsuted valves can cause this condition as well. On the 1997 the valve adjustment is critical and at 190k you shoutld start with the valve adjustment if you can't remember when you had it done last. Once the valves are adjusted use the car to see if the code sets again. If it does, then have a fuel pressure test done; if the pressure is low check the filter and lines before condemning the pump.You need a digital oscilloscope or scan tool to properly test the O2 sensor. I think that's a possibility but its much further down the list than you would think.here's the possible causes in most likely orderValve Clearance needs to be adjustedFuel Pump insufficient flow/pressureFuel Filter cloggedFuel Injector clogged,Fuel Feed Line clogged, leaking or bentFuel Pressure Regulator stuck openPrimary HO2S (Sensor 1) deterioratedEGR System malfunction (too much flow) (egr hung open)Exhaust leak before the O2 sensor (exhaust manifold cracked or leaking manifold gasket)Hope that helps
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Old 24 Jul 2008, 02:06 am
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Default Re: How to fix '97 Accord CEL P0170 & P0171 Codes?

Someone please help me..
I have 97 accord V6 2.7L. I have 298K miles on it. First RPM was jumping when I am driving so I changed the ignition coil, that fixed that but after that I noticed when I put my car to warm up for min or two the RPM going up and down like I am giving gas but I am not even in the car it doing it by itself and this was winter time, now its summer looks like problem is fixed by itself. Now it is summer it does not do that now I have new problem I just started getting this code P0170 and P0171. So I changed the fuel filter, sparkplugs, wire...tune-up. still same code also same problem after tune-up and filter replace now car is doing crazy thing car runs ok for while but 20miles or so and then if I turn my car off and start my car back up it stall and most of the time it would not start it take me 20-50times (I blowup my starter doing that now I have new starter and I don't want to blow that one) before I can get back up running and when I do getting running it will stall and wants to shutdown but I keep pressing gas and it will slowly very slowly start running at same time I would hear some kind of knocking noise from under the car where convertor is( I left the driver side door open I heard it thatís how I know this noise) after that noise is gone car runs like nothing happened. I am thinking it might me MAP sensor or O2 but it might be something else. I need help please help me.
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