LNF/LDK Build with hesitation and turbo kicking in and out under partial throttle

[danrickard]

Fresh LNF/LDK build in 2010 Cobalt SS.

Everything is brand new except Cat, Intercooler and wiring harness.

I have attached 2 logs and if someone is able to take a moment and comment I would appreciate it very much.

Vehicle was running fine and then one day i started getting some knock with hesitation under part throttle. The knock generally happens taking off under load like an incline. The steeper the incline the more the knock. When you accelerate from a stop and "even out" under cruise , if you give it a little gas you can hear a air type sound kick in and if you let off the throttle it goes away. Vac line is tight on BPMV . It is connected straight to intake to aid in diagnosing. When you hear the faint air noise the fuel trims go wacky. If you accelerate hard it evens out and seems to be fine. It's only under light acceleration , at the balance point of cruise/accelerating. I'm new to Hp Tuners and been a mechanic for a few decades and this one has me guessing.

Stock air box with K&N. Present tune is GMS1 for diagnosing purposes. Upper charge pipe and lower charge pipes are aftermarket with zzp intercooler. All couplings are pretty damn tight . Brand new GMS1 Map and Tmap. Tried diff MAF. Tried diff 02 sensor. It's almost like the throttle blade is hanging up or the pedal sensor is not matching the TB sensor? Perhaps someone has seen this before? I tested the BPMV with vacuum and it seemed to hold and released hard when I let go of the Vacuum source. run1saturday.hpllastrunsaturday.hpl

[T-Man]

Can you verify that the fresh air tube nipple isn't broken or leaking on the stock air box? What you're describing sounds like a boost leak.

Hard to tell what the TB is doing because you're not logging desired or commanded.

[danrickard]

Thank you. The nipple isn't broken but good thought. I had the K&N on it first with a custom stainless steel nipple to the updated offset tube....now have the stock box with plastic nipple....I will add the channels and log again. Thank you for taking the time to respond. Still learning. Tried a different Wastegate solenoid today with no difference. Perhaps it's leaking from the nipple to the valve cover or the one way check valve in that is acting up...hope to smoke test tomorrow.

[danrickard]

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