Bank 1 and 2 lean

Tiny
GOVENER71
  • MEMBER
  • 1999 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
1999 GMC SIERRA
Bank 1 and 2 lean are running lean.
I have replaced MAF and checked the Vacuum hoses, Air intake, and PCV.
The SES light is intermitint and will turn on and off every few days.
There is also a slight miss when at an idle but not enough to throw a code.
What should I check next?
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Tuesday, December 7th, 2010 AT 12:48 AM

7 Replies

Tiny
BMRFIXIT
  • EXPERT
What do you have for codes?
Save time and money and have it smoke tested

E85 compatibility is designated for vehicles that are certified to run on up to 85% ethanol and 15% gasoline. All other gasoline engines are designed to run on fuel that contains no more than 10% ethanol.

If using low E85 in a none E 85 certified engine will cause lean condition codes
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Tuesday, December 7th, 2010 AT 1:01 AM
Tiny
GOVENER71
  • MEMBER
I belive the code is P0171 and P0174.

I also only run Mobil or Marathon gas through it and it is all 87 octane accept for the occasional Premium/93.

Will smoke testin act the same as checking the vacuum lines with break cleaner?
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Tuesday, December 7th, 2010 AT 10:12 PM
Tiny
BMRFIXIT
  • EXPERT
Smoke test more accurate than using other methods to check for vacuum leaks
also try and have the injector cleaned
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Wednesday, December 8th, 2010 AT 3:40 AM
Tiny
GOVENER71
  • MEMBER
But would a leaking vac. Line or intake mannifold cause the light to continue to go on and off?
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Sunday, December 12th, 2010 AT 4:04 PM
Tiny
GOVENER71
  • MEMBER
I have been waiting for this to happen again.

I have replaced the MAF, TB gasket, Fuel Filter, Plugs, Wires and all that good stuff.

It has been warm latley, (40-50F) and my truck doesnt throw the P0171 and P0174. But again the other day the temeperature dropped and now the truck is throwing both of those codes again. I have been running at least 83 octane fuel and have looked for vacuum leaks but am not sure of all the vacuum hoses to check. My next step is the replace the EGR valve and the cooland temperature sensor. Would these be a wise decision or what would be casuing the problem?
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Sunday, January 2nd, 2011 AT 3:29 PM
Tiny
BMRFIXIT
  • EXPERT
Should have the injectors cleaned and smoke test the intake manifold for leaks
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Monday, January 3rd, 2011 AT 11:31 PM
Tiny
GOVENER71
  • MEMBER
But if it were a manifold leak would the SES light continue to go on and off over the course of a few days, especially when the weather gets warmer? Seems as though the gasket would either be cracked or not and not cause the light to continue to go on and off.
Also if it were the injectors would I experience a lack of performance in acceleration or power? I currentley am not experienceing any engine difficulty accept for the SES light.
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Tuesday, January 4th, 2011 AT 2:04 AM

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