Can anyone lend some insight on what would cause P0101 code?
4.8L truck engine, (stock)DBW throttle body with LS6 intake. Otherwise stock.
P0101 code has been persistent since I did the swap. Unknown if it was an issue in the truck.
Other, maybe related, symptoms are low idle(550rpm) and very occasional stall.
MAP sensor housing was cracked and replacing this helped with the stalling but P0101 and low idle remain.
A mechanic friend looked at the MAF on a SnapOn scan tool and concluded it was functioning fine. In other words spec seemed to checkout while at idle and respond to throttle input.
We performed a smoke check to look for intake leaks and other than the MAP sensor there were none.
Another possible clue is that before reaching normal coolant temperature, as soon as the car moves, RPMs go to 1200. The moment the car stops engine returns to idle. Once warmed up, this does not happen.
Throttle body is drive by wire and I've done the recalibration procedure once.
Relevant changes performed for the swap are:

1. Truck intake manifold replaced with LS6 (Camero/ Firebird)
2. K&N style air filter. However the MAF is still there and basically in the stock location.
3. No catalytic converters or downstream O2 sensors. Up stream are installed though they are in nonstick locations because of the very custom exhaust.
4. I modified the stock electrical harness. Seems fine given that the MAF data looks good when on a SnapOn scan tool.
5. Currently, both crank case breathers are just venting to atmosphere.

Any thoughts and sugestions would be very helpful.

 

So there is NO PCV system pulling in intake air or having crankcase fumes getting sucked into the intake tract?

 

That's correct. I fail to see how venting to atmosphere could cause the symtoms I'm seeing.

I'm really puzzled by the 1200rpm when rolling.

Phil

 

The higher idle made me suspect it was pulling in air not measured by the MAF.
A vacuum leak would do this also

 

@G Atsma The thing is we actually have a low idle of around 550rpm when the car is stopped. Then once rolling (like as soon as the driveshaft spins) the rpm goes to 1200. In gear or in neutral. Again, this is before reaching full operating temperature. Once warmed up this does not happen but the 550rpm idle remains.

 

I don't really have anything meaningful to add, but that's a cool swap!

What transmission are you running? I did a V6 to 5.3/4L80e swap to my 1999 Silverado and hooked up the transmission speed sensors backwards. I had a high idle of about 1200 rpm. I think my scanner was saying something like 30 MPH while it was in Park and idling. But I figured it out before I got it running. Probably not your case though. But maybe the high idle and the code are 2 separate issues?

 

Thanks for the info and I'm happy with the swap as well. It's my wife's daily driver. Very used 4.8L and 4L60e.
I'll pay more attention to what the ECU reports for vehicle speed . Maybe you're onto something.