[PeteSS2018]

So for a while I've been getting a few codes. Have cleared them but they've come back despite the car mostly running very well (small miss off idle).

Got myself a handy little BlueDriver scanner which works really well. I have three codes it consistently throws together ....

P1516 Command vs Actual Throttle Position Correlation
P0174 & P0171 System too lean on bank 2 & bank 1

I have swapped from my Mamo ported TB back to factory TB, same codes.

The car is running a 2.9L Whipple with custom tune and stock internals. This only started about 3 months ago after having the blower installed for nearly 3 years and change in tune over that time.

I'm suspecting a wiring fault in the TB connector, or an O2 sensor issue.

Suggestions from anyone on where to start?

[PeteSS2018]

Originally Posted by PeteSS2018

So for a while I've been getting a few codes. Have cleared them but they've come back despite the car mostly running very well (small miss off idle).

Got myself a handy little BlueDriver scanner which works really well. I have three codes it consistently throws together ....

P1516 Command vs Actual Throttle Position Correlation
P0174 & P0171 System too lean on bank 2 & bank 1

I have swapped from my Mamo ported TB back to factory TB, same codes.

The car is running a 2.9L Whipple with custom tune and stock internals. This only started about 3 months ago after having the blower installed for nearly 3 years and change in tune over that time.

I'm suspecting a wiring fault in the TB connector, or an O2 sensor issue.

Suggestions from anyone on where to start?

Bump ... hoping for suggestions here

[Joshinator99]

You say you’ve had the blower installed “3 years and change in tune over that time”. So, did this start after a change in tune?

[PeteSS2018]

Originally Posted by Joshinator99

You say you’ve had the blower installed “3 years and change in tune over that time”. So, did this start after a change in tune?

Oops, I meant to say NO change in tune over that time.

Only mod is Mamo ported TB, but I've run the OEM TB also and that made no difference to the codes appearing.

I'm wondering if the accelerator pedal might be a problem with actual vs delivered throttle code problem ....

[laynlo15]

You may have to rescale your MAF tables since you changed TB. Make sure all you connections from your TB to your CAI are tight and no leaks

[KingLT1]

The lean codes indicate that it Might be a vacuum leak...check all the vacuum lines, intake hose connections, and might even check the bolts for the lower manifold on the Supercharger.

[PeteSS2018]

Originally Posted by KingLT1

The lean codes indicate that it Might be a vacuum leak...check all the vacuum lines, intake hose connections, and might even check the bolts for the lower manifold on the Supercharger.

Thanks King. Yes, I'll go over this all again on the weekend in case of a vacuum leak.

I was wondering if an O2 sensor was a problem but seeing as it's both banks 1 & 2 it seems unlikely. Not sure but I have some spares regardless.

Also wondering if the TB electrical connector might be the issue, but I'm not sure how to check this. My gut tells me that the TB and lean codes are connected somehow because they always occur together. But whether I have the Mamo TB or the factory TB on, I get the same code. So perhaps the connector.

I'm also wondering if a dirty MAF sensor, so that's a quick thing to check also, will do this weekend.

Finally I'm also wondering if a bad spark plug would cause the lean codes, I have a very very slight miss off idle which I am suspicious of.

[PeteSS2018]

Originally Posted by laynlo15

You may have to rescale your MAF tables since you changed TB. Make sure all you connections from your TB to your CAI are tight and no leaks

Thanks Laynlo ... Not sure about this. The tune hasn't been changed in 3 years, there was no problem with the throttle relearn procedure when I put the ported TB in, and it was only about 4 months after I swapped the TB that I started getting the CEL with TB/Lean codes.

Since then I have put the factory TB for several weeks but got exactly the same codes.

I don't think this is a tune issue, but it will probably have to go into a shop for a professional to work out.

*** Problem is that here in Australia, there are a grand total of about 1,500 Camaros (SS's and ZL1's) in the whole country so there's no one that really has experience on LT1s or Gen 6 cars.

[PeteSS2018]

A bit more checking today ...

LTFT banks 1 & 2 approx 20 - 27% at 700 rpm (idle).
Drops to about 4% in both banks @ 2,000 rpm.

So I am saying vacuum leak but no obvious signs.

Could it be the catch can? And what else is the easiest way to find a leak?

** Note that I usually get these lean codes with a throttle position code so I also wonder if the throttle plate doesn't quite stay closed at idle.

[KingLT1]

+27% LTFT @ idle on both banks is good indication of a vacuum leak. Both banks going positive indicate leak on the intake side, but I would check exhaust as well.

[PeteSS2018]

Originally Posted by KingLT1

+27% LTFT @ idle on both banks is good indication of a vacuum leak. Both banks going positive indicate leak on the intake side, but I would check exhaust as well.

Thanks KingLT1, my suspicion as well

[PeteSS2018]

Problem solved ....

The good old piece of hose to the hear and listening around all the vacuum lines...

Turns out the low vacuum bypass actuator diaphragm on the supercharger is torn, so was leaking vacuum at idle. Have temporarily plugged the vacuum line and long term fuel trims are back to 6 or 7% on idle.

Thanks KingLT1 and others for comments.

[Joshinator99]

Originally Posted by PeteSS2018

Problem solved ....

The good old piece of hose to the hear and listening around all the vacuum lines...

Turns out the low vacuum bypass actuator diaphragm on the supercharger is torn, so was leaking vacuum at idle. Have temporarily plugged the vacuum line and long term fuel trims are back to 6 or 7% on idle.

Thanks KingLT1 and others for comments.

Very nice! Glad you figured it out. Everyone just wants to read a trouble code and throw parts at stuff these days but there’s no substitute for good old fashioned troubleshooting.

[ZO6Ted]

Just saw this LOL. Was just fixing to tell you to check the Bypass actuator. Happened to my 2.9 3 yrs ago and it was hard to find. Used a stethoscope. Replaced it problem solved. Congrats!