2010 Tahoe/Erratic idle (no codes detected)

Peppy said:

I have a 2010 Tahoe LT with 179xxxx miles that I purchased 3 month ago. My idle is erratic and sometimes stalls when I'm at a stop. It drives fine when I'm on the gas peddle driving it's just when I'm at a stop it goes crazy and sometimes stalls out. I will even put it in neutral while driving it and you can see the idle going crazy and sometime stalls out. I have no engine check light on! I hooked it up to an OBD 2 reader anyways and nothing but when I ran a scan on the engine there are all kinds of codes that pop up from HVAC, o2 sensors, and a few others I can't remember off hand. I'm not very experienced with the scanner but why is the OBD reader not reading anything but the scanner is reading all kinds of codes. I'm using a Foxwell nt501 scanner made for GM trucks

What I have done so far:
- changed out the spark plugs and wires.
- changed out the body throttle and (relearned it to the ECM with a scanner)
- checked the vacuum system by pushing smoke through the system with a smoke machine and I sprayed carb cleaner around the hoses and found nothing.
- changed out the exhaust manifold gasket only because I had to replace the oil pressure sensor
- I reset the Alcohol fuel content because it was showing %17

I'm thinking of replacing the VVT next. I want to change out the water pump anyways just because I don't know if it was ever changed out.

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Doubeleive said:

the 02 sensors are a "sign" and you may want to check fuel pressure and clean the intake and maf

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mikez71 said:

Leaking intake manifold gaskets?
You checked vacuum, but did you spray the base of intake manifold?

Definitely make sure your O2's are good.
Usually if you have a code for those, you would have a check engine light...

When you say idle goes crazy, do you mean it jumps all over the place?
Or is it only stumbling/stalling?

Also try to record the actual codes.
FWIW I regularly see 10+% ethanol on regular gas..

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Peppy said:

Thanks for the response. I forgot the mention in my original post that I did clean the MAF and intake. For my truck to run that bad I figured the engine check light would go on. I'm new the scanner world so I don't know how accurate the scanner is when the truck isn't throwing any codes. Should I trust it and change out the 02 sensors? I'm using a Foxwell nt501 elite

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Peppy said:

I figured putting smoke through the vacuum system would show if the intake is leaking, plus I did spray the base of the intake manifold, and everything is fine.

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