Dustin Glover

Hello everyone,

I just bought a beautiful 2009 C6 with less than 10k miles. CEL came on about 200 miles into my drive home from buying it.
P0171 & P0174 Lean on both banks.
First off it does have the following mods:

Z06 manifolds (GM original)
Z06 cats (GM original)
Z06 H-pipe (GM original)
Z06 mufflers (GM original)
NPP (exhaust control) Mild to wild.
Halltech Intake
Halltech Intake shroud
160* thermostat
Professionally tuned for hp/mpg/160*/91 octane/!CAGS

Everything was professionally installed and the car runs damn good under moderate to WOT. I took it to my specialist the other day and he cleaned the maf, smoked it to look for leaks and didn't find any. Here are the symptoms. Idle is all over the place. It will hunt anywhere from 550-750 rpm at a stop light. There is a very slight hesitation at light throttle, goes away with a tiny bit more throttle and as mentioned above at moderate or full throttle it's perfect!

I removed the Halltech shroud since it would seem to be able to breathe much better without it. It slightly helped smooth out the idle some, but the CEL came back, so I reinstalled it.
Could it still be the MAF is bad? Thinking of just having it retuned and adjust the fuel trims so I don't get the CEL? I've searched the forums and see that it is very common to get these lean codes on cars with an intake. What should I do? The car only has 10k flippin miles. The first CEL on my Yukon came on at 198k miles.

cclive

Fair enough but you probably didn't replace all those intake and exhaust parts on the Yukon with parts not designed for its' engine. It may take some trial and error adjustments to make things work right.

Dustin Glover

Finally figured it out. It was a bad tune. Car is running great now after a fresh tune. The idle still isn't perfect though. Is it just the nature of the ls3 to idle between 600-700 rpms?