2001 Aurora throwing codes

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  #1  
Old 07-13-14, 03:22 PM
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2001 Aurora throwing codes

I have a 2001 Aurora, 91000 mi., 8 cyl. ( Northstar engine ) Throwing two codes. PO171 (system to lean Bank 1) and PO174 ( system to lean Bank 2 ) anyone have any ideas what could be causing these. My wife said it is running rough at times and when she is at a stop sign it is surging. Any help would be appreciated.
 
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Old 07-13-14, 04:17 PM
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OBD-II DTC: P0171 System Too Lean (Bank 1)

My bet is on sticky injectors. Run Seafoam through tankful.
 
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Old 07-13-14, 05:04 PM
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Where did you have the codes tested? Could you also give us some live data? Such as fuel trims bank 1 & 2 and your O2A1 and O2B1 sensor readings?

It could also be a vacuum leak anywhere past the MAF sensor- intake or emissions. Vacuum leaks will make the engine think it's running lean due to the excessive amount of air, the computer would think it has to compensate for it by sending more fuel.

Could also be a restricted fuel filter or low fuel pressure, but probably not as likely.
 
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Old 07-13-14, 05:30 PM
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Could be time for new O2 sensors.
 
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Old 07-13-14, 06:04 PM
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To check the O2 sensors, you really only need to pay attention to the front ones A1 & B1, since the rear ones A2 and B2 are past the catalytic converter they are not a factor in setting the engine codes or in the computer controlled fuel/spark adjustments. When viewed as a graph, the O2 sensors should be giving alternating voltage signals, high and low (somewhere between .1V and .8V, with a median of .42V) which will look like a repeating sine wave. Your O2 sensors readings will average below the median, which indicates a lean condition- we just don't know HOW low those readings are without the live data. If your live data graph is oscillating and only looks slightly below the median, your O2 sensors are fine.

Even if your O2 sensors show consistently low voltage (lean), it does not necessarily mean the O2 sensor is the problem. (serious O2 problems will usually throw an O2 code) A person might assume they are toast, but that's not always the case- it could mean they are reading accurately, and are detecting a massive vacuum leak. If the O2 numbers seem low (and flat) at idle, but improve (and oscillate) at highways speeds, that's a classic symptom of a vacuum leak. This is tested by a 2nd person checking the live data on the OBD-II scanner while you are at idle v.s. being on a test drive.

Cleaning the MAF sensor would be number one, IMO, (cost- $5 for a spray can of MAF cleaner) and looking for a vacuum leak won't cost a dime. It will just take you a while to look all the hoses and connectors over.

Codes must eventually be reset to see if the problem reoccurs.
 
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Old 07-13-14, 08:44 PM
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I did reset the codes, have to wait til tomorrow when the wife drives it to work to see if they re-occur. Thanks
 
  #7  
Old 07-13-14, 08:49 PM
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I checked the codes myself, I'll have to wait til tomorrow to get the fuel trim readings. Thanks
 
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