Need help with lean code p0171

[04BlackMagic]

05 Tahoe 5.3 LM7 has constant code P0171 and p0300. Scan tool data shows misfire on all cylinders in bank 1. Cylinder 1 is the worst. Constant misfire almost as if cylinder dead. Check engine light flashing. Exhaust doesn't smell right. Any help would be appreciated! Have a bunch of other codes but want to get to bottoms of this one. Will upload media shortly

 

Thanks

 

 

 

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[04BlackMagic]

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[04BlackMagic]

Exhaust tip is covered in a white powder???


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[sefiroxx]

If it is the whole bank, then sounds like a wiring short.

Try running at night with a mister to see if there is any arcing.

[04BlackMagic]

Thanks


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[Supreme Pizza]

   The first step in the diagnostic procedure, would be to find a common link between these codes, especially if they all happened at once. You would want to read through the links below, and try to find a common possible cause. If most of the codes share a possible cause of "plugged fuel filter", then that would be a good place to start. If you cant find a common possible cause, then you would want to start at the top of the ladder, and work your way down - meaning that you need to prioritize the issues. Your O2 sensor codes could be a symptom of another problem, or they could be the cause of a problem. Try to fix the things that are not a possible symptom first. If you replace the O2's, and the codes were actually a symptom of another issue, then you accomplished nothing. Also, don't be afraid to clear the codes, and see which ones come back. Many times, some of the codes don't return, either because the code was a fluke, or because the computer reverted to factory defaults and stopped looking for signals from that sensor after detecting an unexpected value, and if its not looking at the sensor readings, the computer will never automatically test that sensor again until the codes are cleared. 

 

https://www.autocodes.com/p0300_chevrolet.html

 

https://www.autocodes.com/p1133_chevrolet.html

 

https://www.autocodes.com/p0171_chevrolet.html

 

https://www.engine-codes.com/p1626_chevrolet.html

 

https://www.2carpros.com/questions/2003-chevrolet-impala-code-u1064

 

https://www.obd-codes.com/p0131

[04BlackMagic]

Thank you for info. I believe the two oxygen sensors and misfire code are result of p0171. I think there is intake leak somewhere but need to smog test to confirm.


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[Supreme Pizza]

You can find intake leaks using starting fluid. Make sure the engine is cold, and then start the motor. Spray the starting fluid around all the gaskets on the intake manifold, vacuum hoses, intake tube etc. If the engine revs up, you have a leak. You can also find it using a smoker. 

 

Yes, yes, I know - people will say DON'T USE STARTING FLUID!

 

The people that say NOT to use starting fluid that way are 100% correct (according to the instructions on the can). 

 

People that DO use starting fluid that way have been doing it for years without any problem. 

 

 

Obviously you should have a fire extinguisher handy, only do it on a cold engine, and don't SOAK the engine. Just use light little puffs of starting fluid. If anything starts to get wet, wait a minute for it to evaporate before you continue. Only do this outside, never in a garage. 

 

 

[04BlackMagic]

Yes I have tried this and no luck. Need to use a smoker. Believe there is vacuum leak at bottom of intake manifold


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[Supreme Pizza]

If your going after P0171, I would not start with a vacuum leak unless it has a high/wandering idle. 

 

I would start here: 

 

Check/clean the PCV valve and tube

Clean the Mass air flow sensor 

Add some strong fuel injector cleaner 

Check fuel pressure

 

 

Those are quick easy things to check, and just generally good maintenance items to do anyway.  

 

Then I would move on to other stuff. I just like starting with the easiest quickest thing first. Sometimes it pays off. 

 

[riverbanks]

Curious about the white exhaust,any progress?one thing to do would be swap front 02's,see if code stays with the bank or swaps with it

[Supreme Pizza]

1 hour ago, riverbanks said:

one thing to do would be swap front 02's,see if code stays with the bank or swaps with it

 

  Good tip. 

[riverbanks]

Or how about the screwdriver to ear test, other end on injector,listen for clicking, check them all to learn the proper sound

[04BlackMagic]

Problem was faulty B1 S1 oxygen sensor

Replaced with OEM Denso sensor

Cleared codes, no issues with engine, no misfires, exhaust smell and smoke went away

Thanks to all who left responses!!!


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